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![Jiri Pirko](/assets/img/avatar_default.png)
Use previously introduced list_entry_rcu instead of an open-coded list_entry + rcu_dereference combination. Signed-off-by: Jiri Pirko <jpirko@redhat.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: dipankar@in.ibm.com LKML-Reference: <20090414181715.GA3634@psychotron.englab.brq.redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1380 lines
34 KiB
C
1380 lines
34 KiB
C
/*
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* linux/ipc/sem.c
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* Copyright (C) 1992 Krishna Balasubramanian
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* Copyright (C) 1995 Eric Schenk, Bruno Haible
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*
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* IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
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* This code underwent a massive rewrite in order to solve some problems
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* with the original code. In particular the original code failed to
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* wake up processes that were waiting for semval to go to 0 if the
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* value went to 0 and was then incremented rapidly enough. In solving
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* this problem I have also modified the implementation so that it
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* processes pending operations in a FIFO manner, thus give a guarantee
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* that processes waiting for a lock on the semaphore won't starve
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* unless another locking process fails to unlock.
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* In addition the following two changes in behavior have been introduced:
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* - The original implementation of semop returned the value
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* last semaphore element examined on success. This does not
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* match the manual page specifications, and effectively
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* allows the user to read the semaphore even if they do not
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* have read permissions. The implementation now returns 0
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* on success as stated in the manual page.
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* - There is some confusion over whether the set of undo adjustments
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* to be performed at exit should be done in an atomic manner.
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* That is, if we are attempting to decrement the semval should we queue
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* up and wait until we can do so legally?
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* The original implementation attempted to do this.
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* The current implementation does not do so. This is because I don't
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* think it is the right thing (TM) to do, and because I couldn't
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* see a clean way to get the old behavior with the new design.
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* The POSIX standard and SVID should be consulted to determine
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* what behavior is mandated.
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*
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* Further notes on refinement (Christoph Rohland, December 1998):
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* - The POSIX standard says, that the undo adjustments simply should
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* redo. So the current implementation is o.K.
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* - The previous code had two flaws:
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* 1) It actively gave the semaphore to the next waiting process
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* sleeping on the semaphore. Since this process did not have the
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* cpu this led to many unnecessary context switches and bad
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* performance. Now we only check which process should be able to
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* get the semaphore and if this process wants to reduce some
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* semaphore value we simply wake it up without doing the
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* operation. So it has to try to get it later. Thus e.g. the
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* running process may reacquire the semaphore during the current
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* time slice. If it only waits for zero or increases the semaphore,
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* we do the operation in advance and wake it up.
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* 2) It did not wake up all zero waiting processes. We try to do
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* better but only get the semops right which only wait for zero or
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* increase. If there are decrement operations in the operations
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* array we do the same as before.
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*
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* With the incarnation of O(1) scheduler, it becomes unnecessary to perform
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* check/retry algorithm for waking up blocked processes as the new scheduler
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* is better at handling thread switch than the old one.
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*
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* /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
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*
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* SMP-threaded, sysctl's added
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* (c) 1999 Manfred Spraul <manfred@colorfullife.com>
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* Enforced range limit on SEM_UNDO
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* (c) 2001 Red Hat Inc
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* Lockless wakeup
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* (c) 2003 Manfred Spraul <manfred@colorfullife.com>
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*
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* support for audit of ipc object properties and permission changes
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* Dustin Kirkland <dustin.kirkland@us.ibm.com>
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*
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* namespaces support
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* OpenVZ, SWsoft Inc.
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* Pavel Emelianov <xemul@openvz.org>
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*/
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/init.h>
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#include <linux/proc_fs.h>
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#include <linux/time.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/audit.h>
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#include <linux/capability.h>
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#include <linux/seq_file.h>
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#include <linux/rwsem.h>
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#include <linux/nsproxy.h>
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#include <linux/ipc_namespace.h>
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#include <asm/uaccess.h>
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#include "util.h"
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#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
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#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
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#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
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static int newary(struct ipc_namespace *, struct ipc_params *);
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static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
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#ifdef CONFIG_PROC_FS
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static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
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#endif
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#define SEMMSL_FAST 256 /* 512 bytes on stack */
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#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
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/*
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* linked list protection:
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* sem_undo.id_next,
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* sem_array.sem_pending{,last},
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* sem_array.sem_undo: sem_lock() for read/write
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* sem_undo.proc_next: only "current" is allowed to read/write that field.
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*
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*/
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#define sc_semmsl sem_ctls[0]
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#define sc_semmns sem_ctls[1]
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#define sc_semopm sem_ctls[2]
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#define sc_semmni sem_ctls[3]
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void sem_init_ns(struct ipc_namespace *ns)
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{
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ns->sc_semmsl = SEMMSL;
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ns->sc_semmns = SEMMNS;
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ns->sc_semopm = SEMOPM;
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ns->sc_semmni = SEMMNI;
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ns->used_sems = 0;
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ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
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}
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#ifdef CONFIG_IPC_NS
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void sem_exit_ns(struct ipc_namespace *ns)
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{
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free_ipcs(ns, &sem_ids(ns), freeary);
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}
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#endif
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void __init sem_init (void)
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{
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sem_init_ns(&init_ipc_ns);
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ipc_init_proc_interface("sysvipc/sem",
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" key semid perms nsems uid gid cuid cgid otime ctime\n",
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IPC_SEM_IDS, sysvipc_sem_proc_show);
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}
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/*
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* sem_lock_(check_) routines are called in the paths where the rw_mutex
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* is not held.
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*/
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static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
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{
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struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
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if (IS_ERR(ipcp))
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return (struct sem_array *)ipcp;
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return container_of(ipcp, struct sem_array, sem_perm);
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}
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static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
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int id)
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{
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struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
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if (IS_ERR(ipcp))
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return (struct sem_array *)ipcp;
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return container_of(ipcp, struct sem_array, sem_perm);
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}
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static inline void sem_lock_and_putref(struct sem_array *sma)
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{
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ipc_lock_by_ptr(&sma->sem_perm);
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ipc_rcu_putref(sma);
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}
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static inline void sem_getref_and_unlock(struct sem_array *sma)
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{
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ipc_rcu_getref(sma);
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ipc_unlock(&(sma)->sem_perm);
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}
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static inline void sem_putref(struct sem_array *sma)
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{
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ipc_lock_by_ptr(&sma->sem_perm);
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ipc_rcu_putref(sma);
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ipc_unlock(&(sma)->sem_perm);
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}
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static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
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{
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ipc_rmid(&sem_ids(ns), &s->sem_perm);
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}
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/*
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* Lockless wakeup algorithm:
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* Without the check/retry algorithm a lockless wakeup is possible:
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* - queue.status is initialized to -EINTR before blocking.
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* - wakeup is performed by
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* * unlinking the queue entry from sma->sem_pending
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* * setting queue.status to IN_WAKEUP
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* This is the notification for the blocked thread that a
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* result value is imminent.
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* * call wake_up_process
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* * set queue.status to the final value.
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* - the previously blocked thread checks queue.status:
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* * if it's IN_WAKEUP, then it must wait until the value changes
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* * if it's not -EINTR, then the operation was completed by
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* update_queue. semtimedop can return queue.status without
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* performing any operation on the sem array.
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* * otherwise it must acquire the spinlock and check what's up.
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*
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* The two-stage algorithm is necessary to protect against the following
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* races:
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* - if queue.status is set after wake_up_process, then the woken up idle
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* thread could race forward and try (and fail) to acquire sma->lock
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* before update_queue had a chance to set queue.status
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* - if queue.status is written before wake_up_process and if the
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* blocked process is woken up by a signal between writing
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* queue.status and the wake_up_process, then the woken up
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* process could return from semtimedop and die by calling
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* sys_exit before wake_up_process is called. Then wake_up_process
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* will oops, because the task structure is already invalid.
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* (yes, this happened on s390 with sysv msg).
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*
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*/
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#define IN_WAKEUP 1
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/**
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* newary - Create a new semaphore set
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* @ns: namespace
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* @params: ptr to the structure that contains key, semflg and nsems
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*
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* Called with sem_ids.rw_mutex held (as a writer)
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*/
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static int newary(struct ipc_namespace *ns, struct ipc_params *params)
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{
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int id;
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int retval;
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struct sem_array *sma;
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int size;
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key_t key = params->key;
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int nsems = params->u.nsems;
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int semflg = params->flg;
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if (!nsems)
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return -EINVAL;
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if (ns->used_sems + nsems > ns->sc_semmns)
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return -ENOSPC;
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size = sizeof (*sma) + nsems * sizeof (struct sem);
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sma = ipc_rcu_alloc(size);
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if (!sma) {
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return -ENOMEM;
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}
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memset (sma, 0, size);
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sma->sem_perm.mode = (semflg & S_IRWXUGO);
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sma->sem_perm.key = key;
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sma->sem_perm.security = NULL;
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retval = security_sem_alloc(sma);
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if (retval) {
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ipc_rcu_putref(sma);
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return retval;
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}
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id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
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if (id < 0) {
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security_sem_free(sma);
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ipc_rcu_putref(sma);
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return id;
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}
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ns->used_sems += nsems;
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sma->sem_base = (struct sem *) &sma[1];
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INIT_LIST_HEAD(&sma->sem_pending);
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INIT_LIST_HEAD(&sma->list_id);
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sma->sem_nsems = nsems;
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sma->sem_ctime = get_seconds();
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sem_unlock(sma);
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return sma->sem_perm.id;
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}
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/*
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* Called with sem_ids.rw_mutex and ipcp locked.
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*/
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static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
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{
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struct sem_array *sma;
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sma = container_of(ipcp, struct sem_array, sem_perm);
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return security_sem_associate(sma, semflg);
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}
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/*
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* Called with sem_ids.rw_mutex and ipcp locked.
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*/
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static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
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struct ipc_params *params)
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{
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struct sem_array *sma;
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sma = container_of(ipcp, struct sem_array, sem_perm);
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if (params->u.nsems > sma->sem_nsems)
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return -EINVAL;
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return 0;
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}
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SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
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{
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struct ipc_namespace *ns;
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struct ipc_ops sem_ops;
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struct ipc_params sem_params;
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ns = current->nsproxy->ipc_ns;
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if (nsems < 0 || nsems > ns->sc_semmsl)
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return -EINVAL;
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sem_ops.getnew = newary;
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sem_ops.associate = sem_security;
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sem_ops.more_checks = sem_more_checks;
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sem_params.key = key;
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sem_params.flg = semflg;
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sem_params.u.nsems = nsems;
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return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
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}
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/*
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* Determine whether a sequence of semaphore operations would succeed
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* all at once. Return 0 if yes, 1 if need to sleep, else return error code.
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*/
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static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
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int nsops, struct sem_undo *un, int pid)
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{
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int result, sem_op;
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struct sembuf *sop;
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struct sem * curr;
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for (sop = sops; sop < sops + nsops; sop++) {
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curr = sma->sem_base + sop->sem_num;
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sem_op = sop->sem_op;
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result = curr->semval;
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if (!sem_op && result)
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goto would_block;
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result += sem_op;
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if (result < 0)
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goto would_block;
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if (result > SEMVMX)
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goto out_of_range;
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if (sop->sem_flg & SEM_UNDO) {
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int undo = un->semadj[sop->sem_num] - sem_op;
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/*
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* Exceeding the undo range is an error.
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*/
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if (undo < (-SEMAEM - 1) || undo > SEMAEM)
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goto out_of_range;
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}
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curr->semval = result;
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}
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sop--;
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while (sop >= sops) {
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sma->sem_base[sop->sem_num].sempid = pid;
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if (sop->sem_flg & SEM_UNDO)
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un->semadj[sop->sem_num] -= sop->sem_op;
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sop--;
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}
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sma->sem_otime = get_seconds();
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return 0;
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out_of_range:
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result = -ERANGE;
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goto undo;
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would_block:
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if (sop->sem_flg & IPC_NOWAIT)
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result = -EAGAIN;
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else
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result = 1;
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undo:
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sop--;
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while (sop >= sops) {
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sma->sem_base[sop->sem_num].semval -= sop->sem_op;
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sop--;
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}
|
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|
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return result;
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}
|
|
|
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/* Go through the pending queue for the indicated semaphore
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* looking for tasks that can be completed.
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*/
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static void update_queue (struct sem_array * sma)
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{
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int error;
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struct sem_queue * q;
|
|
|
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q = list_entry(sma->sem_pending.next, struct sem_queue, list);
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while (&q->list != &sma->sem_pending) {
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error = try_atomic_semop(sma, q->sops, q->nsops,
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q->undo, q->pid);
|
|
|
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/* Does q->sleeper still need to sleep? */
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if (error <= 0) {
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struct sem_queue *n;
|
|
|
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/*
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* Continue scanning. The next operation
|
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* that must be checked depends on the type of the
|
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* completed operation:
|
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* - if the operation modified the array, then
|
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* restart from the head of the queue and
|
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* check for threads that might be waiting
|
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* for semaphore values to become 0.
|
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* - if the operation didn't modify the array,
|
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* then just continue.
|
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* The order of list_del() and reading ->next
|
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* is crucial: In the former case, the list_del()
|
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* must be done first [because we might be the
|
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* first entry in ->sem_pending], in the latter
|
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* case the list_del() must be done last
|
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* [because the list is invalid after the list_del()]
|
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*/
|
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if (q->alter) {
|
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list_del(&q->list);
|
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n = list_entry(sma->sem_pending.next,
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struct sem_queue, list);
|
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} else {
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n = list_entry(q->list.next, struct sem_queue,
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list);
|
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list_del(&q->list);
|
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}
|
|
|
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/* wake up the waiting thread */
|
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q->status = IN_WAKEUP;
|
|
|
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wake_up_process(q->sleeper);
|
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/* hands-off: q will disappear immediately after
|
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* writing q->status.
|
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*/
|
|
smp_wmb();
|
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q->status = error;
|
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q = n;
|
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} else {
|
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q = list_entry(q->list.next, struct sem_queue, list);
|
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}
|
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}
|
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}
|
|
|
|
/* The following counts are associated to each semaphore:
|
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* semncnt number of tasks waiting on semval being nonzero
|
|
* semzcnt number of tasks waiting on semval being zero
|
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* This model assumes that a task waits on exactly one semaphore.
|
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* Since semaphore operations are to be performed atomically, tasks actually
|
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* wait on a whole sequence of semaphores simultaneously.
|
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* The counts we return here are a rough approximation, but still
|
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* warrant that semncnt+semzcnt>0 if the task is on the pending queue.
|
|
*/
|
|
static int count_semncnt (struct sem_array * sma, ushort semnum)
|
|
{
|
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int semncnt;
|
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struct sem_queue * q;
|
|
|
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semncnt = 0;
|
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list_for_each_entry(q, &sma->sem_pending, list) {
|
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struct sembuf * sops = q->sops;
|
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int nsops = q->nsops;
|
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int i;
|
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for (i = 0; i < nsops; i++)
|
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if (sops[i].sem_num == semnum
|
|
&& (sops[i].sem_op < 0)
|
|
&& !(sops[i].sem_flg & IPC_NOWAIT))
|
|
semncnt++;
|
|
}
|
|
return semncnt;
|
|
}
|
|
|
|
static int count_semzcnt (struct sem_array * sma, ushort semnum)
|
|
{
|
|
int semzcnt;
|
|
struct sem_queue * q;
|
|
|
|
semzcnt = 0;
|
|
list_for_each_entry(q, &sma->sem_pending, list) {
|
|
struct sembuf * sops = q->sops;
|
|
int nsops = q->nsops;
|
|
int i;
|
|
for (i = 0; i < nsops; i++)
|
|
if (sops[i].sem_num == semnum
|
|
&& (sops[i].sem_op == 0)
|
|
&& !(sops[i].sem_flg & IPC_NOWAIT))
|
|
semzcnt++;
|
|
}
|
|
return semzcnt;
|
|
}
|
|
|
|
static void free_un(struct rcu_head *head)
|
|
{
|
|
struct sem_undo *un = container_of(head, struct sem_undo, rcu);
|
|
kfree(un);
|
|
}
|
|
|
|
/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
|
|
* as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
|
|
* remains locked on exit.
|
|
*/
|
|
static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
|
|
{
|
|
struct sem_undo *un, *tu;
|
|
struct sem_queue *q, *tq;
|
|
struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
|
|
/* Free the existing undo structures for this semaphore set. */
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
|
|
list_del(&un->list_id);
|
|
spin_lock(&un->ulp->lock);
|
|
un->semid = -1;
|
|
list_del_rcu(&un->list_proc);
|
|
spin_unlock(&un->ulp->lock);
|
|
call_rcu(&un->rcu, free_un);
|
|
}
|
|
|
|
/* Wake up all pending processes and let them fail with EIDRM. */
|
|
list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
|
|
list_del(&q->list);
|
|
|
|
q->status = IN_WAKEUP;
|
|
wake_up_process(q->sleeper); /* doesn't sleep */
|
|
smp_wmb();
|
|
q->status = -EIDRM; /* hands-off q */
|
|
}
|
|
|
|
/* Remove the semaphore set from the IDR */
|
|
sem_rmid(ns, sma);
|
|
sem_unlock(sma);
|
|
|
|
ns->used_sems -= sma->sem_nsems;
|
|
security_sem_free(sma);
|
|
ipc_rcu_putref(sma);
|
|
}
|
|
|
|
static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
|
|
{
|
|
switch(version) {
|
|
case IPC_64:
|
|
return copy_to_user(buf, in, sizeof(*in));
|
|
case IPC_OLD:
|
|
{
|
|
struct semid_ds out;
|
|
|
|
ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
|
|
|
|
out.sem_otime = in->sem_otime;
|
|
out.sem_ctime = in->sem_ctime;
|
|
out.sem_nsems = in->sem_nsems;
|
|
|
|
return copy_to_user(buf, &out, sizeof(out));
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
static int semctl_nolock(struct ipc_namespace *ns, int semid,
|
|
int cmd, int version, union semun arg)
|
|
{
|
|
int err = -EINVAL;
|
|
struct sem_array *sma;
|
|
|
|
switch(cmd) {
|
|
case IPC_INFO:
|
|
case SEM_INFO:
|
|
{
|
|
struct seminfo seminfo;
|
|
int max_id;
|
|
|
|
err = security_sem_semctl(NULL, cmd);
|
|
if (err)
|
|
return err;
|
|
|
|
memset(&seminfo,0,sizeof(seminfo));
|
|
seminfo.semmni = ns->sc_semmni;
|
|
seminfo.semmns = ns->sc_semmns;
|
|
seminfo.semmsl = ns->sc_semmsl;
|
|
seminfo.semopm = ns->sc_semopm;
|
|
seminfo.semvmx = SEMVMX;
|
|
seminfo.semmnu = SEMMNU;
|
|
seminfo.semmap = SEMMAP;
|
|
seminfo.semume = SEMUME;
|
|
down_read(&sem_ids(ns).rw_mutex);
|
|
if (cmd == SEM_INFO) {
|
|
seminfo.semusz = sem_ids(ns).in_use;
|
|
seminfo.semaem = ns->used_sems;
|
|
} else {
|
|
seminfo.semusz = SEMUSZ;
|
|
seminfo.semaem = SEMAEM;
|
|
}
|
|
max_id = ipc_get_maxid(&sem_ids(ns));
|
|
up_read(&sem_ids(ns).rw_mutex);
|
|
if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
|
|
return -EFAULT;
|
|
return (max_id < 0) ? 0: max_id;
|
|
}
|
|
case IPC_STAT:
|
|
case SEM_STAT:
|
|
{
|
|
struct semid64_ds tbuf;
|
|
int id;
|
|
|
|
if (cmd == SEM_STAT) {
|
|
sma = sem_lock(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return PTR_ERR(sma);
|
|
id = sma->sem_perm.id;
|
|
} else {
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return PTR_ERR(sma);
|
|
id = 0;
|
|
}
|
|
|
|
err = -EACCES;
|
|
if (ipcperms (&sma->sem_perm, S_IRUGO))
|
|
goto out_unlock;
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock;
|
|
|
|
memset(&tbuf, 0, sizeof(tbuf));
|
|
|
|
kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
|
|
tbuf.sem_otime = sma->sem_otime;
|
|
tbuf.sem_ctime = sma->sem_ctime;
|
|
tbuf.sem_nsems = sma->sem_nsems;
|
|
sem_unlock(sma);
|
|
if (copy_semid_to_user (arg.buf, &tbuf, version))
|
|
return -EFAULT;
|
|
return id;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
return err;
|
|
out_unlock:
|
|
sem_unlock(sma);
|
|
return err;
|
|
}
|
|
|
|
static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
|
|
int cmd, int version, union semun arg)
|
|
{
|
|
struct sem_array *sma;
|
|
struct sem* curr;
|
|
int err;
|
|
ushort fast_sem_io[SEMMSL_FAST];
|
|
ushort* sem_io = fast_sem_io;
|
|
int nsems;
|
|
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return PTR_ERR(sma);
|
|
|
|
nsems = sma->sem_nsems;
|
|
|
|
err = -EACCES;
|
|
if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
|
|
goto out_unlock;
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock;
|
|
|
|
err = -EACCES;
|
|
switch (cmd) {
|
|
case GETALL:
|
|
{
|
|
ushort __user *array = arg.array;
|
|
int i;
|
|
|
|
if(nsems > SEMMSL_FAST) {
|
|
sem_getref_and_unlock(sma);
|
|
|
|
sem_io = ipc_alloc(sizeof(ushort)*nsems);
|
|
if(sem_io == NULL) {
|
|
sem_putref(sma);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
sem_lock_and_putref(sma);
|
|
if (sma->sem_perm.deleted) {
|
|
sem_unlock(sma);
|
|
err = -EIDRM;
|
|
goto out_free;
|
|
}
|
|
}
|
|
|
|
for (i = 0; i < sma->sem_nsems; i++)
|
|
sem_io[i] = sma->sem_base[i].semval;
|
|
sem_unlock(sma);
|
|
err = 0;
|
|
if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
|
|
err = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
case SETALL:
|
|
{
|
|
int i;
|
|
struct sem_undo *un;
|
|
|
|
sem_getref_and_unlock(sma);
|
|
|
|
if(nsems > SEMMSL_FAST) {
|
|
sem_io = ipc_alloc(sizeof(ushort)*nsems);
|
|
if(sem_io == NULL) {
|
|
sem_putref(sma);
|
|
return -ENOMEM;
|
|
}
|
|
}
|
|
|
|
if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
|
|
sem_putref(sma);
|
|
err = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
|
|
for (i = 0; i < nsems; i++) {
|
|
if (sem_io[i] > SEMVMX) {
|
|
sem_putref(sma);
|
|
err = -ERANGE;
|
|
goto out_free;
|
|
}
|
|
}
|
|
sem_lock_and_putref(sma);
|
|
if (sma->sem_perm.deleted) {
|
|
sem_unlock(sma);
|
|
err = -EIDRM;
|
|
goto out_free;
|
|
}
|
|
|
|
for (i = 0; i < nsems; i++)
|
|
sma->sem_base[i].semval = sem_io[i];
|
|
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_for_each_entry(un, &sma->list_id, list_id) {
|
|
for (i = 0; i < nsems; i++)
|
|
un->semadj[i] = 0;
|
|
}
|
|
sma->sem_ctime = get_seconds();
|
|
/* maybe some queued-up processes were waiting for this */
|
|
update_queue(sma);
|
|
err = 0;
|
|
goto out_unlock;
|
|
}
|
|
/* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
|
|
}
|
|
err = -EINVAL;
|
|
if(semnum < 0 || semnum >= nsems)
|
|
goto out_unlock;
|
|
|
|
curr = &sma->sem_base[semnum];
|
|
|
|
switch (cmd) {
|
|
case GETVAL:
|
|
err = curr->semval;
|
|
goto out_unlock;
|
|
case GETPID:
|
|
err = curr->sempid;
|
|
goto out_unlock;
|
|
case GETNCNT:
|
|
err = count_semncnt(sma,semnum);
|
|
goto out_unlock;
|
|
case GETZCNT:
|
|
err = count_semzcnt(sma,semnum);
|
|
goto out_unlock;
|
|
case SETVAL:
|
|
{
|
|
int val = arg.val;
|
|
struct sem_undo *un;
|
|
|
|
err = -ERANGE;
|
|
if (val > SEMVMX || val < 0)
|
|
goto out_unlock;
|
|
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_for_each_entry(un, &sma->list_id, list_id)
|
|
un->semadj[semnum] = 0;
|
|
|
|
curr->semval = val;
|
|
curr->sempid = task_tgid_vnr(current);
|
|
sma->sem_ctime = get_seconds();
|
|
/* maybe some queued-up processes were waiting for this */
|
|
update_queue(sma);
|
|
err = 0;
|
|
goto out_unlock;
|
|
}
|
|
}
|
|
out_unlock:
|
|
sem_unlock(sma);
|
|
out_free:
|
|
if(sem_io != fast_sem_io)
|
|
ipc_free(sem_io, sizeof(ushort)*nsems);
|
|
return err;
|
|
}
|
|
|
|
static inline unsigned long
|
|
copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
|
|
{
|
|
switch(version) {
|
|
case IPC_64:
|
|
if (copy_from_user(out, buf, sizeof(*out)))
|
|
return -EFAULT;
|
|
return 0;
|
|
case IPC_OLD:
|
|
{
|
|
struct semid_ds tbuf_old;
|
|
|
|
if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
|
|
return -EFAULT;
|
|
|
|
out->sem_perm.uid = tbuf_old.sem_perm.uid;
|
|
out->sem_perm.gid = tbuf_old.sem_perm.gid;
|
|
out->sem_perm.mode = tbuf_old.sem_perm.mode;
|
|
|
|
return 0;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This function handles some semctl commands which require the rw_mutex
|
|
* to be held in write mode.
|
|
* NOTE: no locks must be held, the rw_mutex is taken inside this function.
|
|
*/
|
|
static int semctl_down(struct ipc_namespace *ns, int semid,
|
|
int cmd, int version, union semun arg)
|
|
{
|
|
struct sem_array *sma;
|
|
int err;
|
|
struct semid64_ds semid64;
|
|
struct kern_ipc_perm *ipcp;
|
|
|
|
if(cmd == IPC_SET) {
|
|
if (copy_semid_from_user(&semid64, arg.buf, version))
|
|
return -EFAULT;
|
|
}
|
|
|
|
ipcp = ipcctl_pre_down(&sem_ids(ns), semid, cmd, &semid64.sem_perm, 0);
|
|
if (IS_ERR(ipcp))
|
|
return PTR_ERR(ipcp);
|
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock;
|
|
|
|
switch(cmd){
|
|
case IPC_RMID:
|
|
freeary(ns, ipcp);
|
|
goto out_up;
|
|
case IPC_SET:
|
|
ipc_update_perm(&semid64.sem_perm, ipcp);
|
|
sma->sem_ctime = get_seconds();
|
|
break;
|
|
default:
|
|
err = -EINVAL;
|
|
}
|
|
|
|
out_unlock:
|
|
sem_unlock(sma);
|
|
out_up:
|
|
up_write(&sem_ids(ns).rw_mutex);
|
|
return err;
|
|
}
|
|
|
|
SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
|
|
{
|
|
int err = -EINVAL;
|
|
int version;
|
|
struct ipc_namespace *ns;
|
|
|
|
if (semid < 0)
|
|
return -EINVAL;
|
|
|
|
version = ipc_parse_version(&cmd);
|
|
ns = current->nsproxy->ipc_ns;
|
|
|
|
switch(cmd) {
|
|
case IPC_INFO:
|
|
case SEM_INFO:
|
|
case IPC_STAT:
|
|
case SEM_STAT:
|
|
err = semctl_nolock(ns, semid, cmd, version, arg);
|
|
return err;
|
|
case GETALL:
|
|
case GETVAL:
|
|
case GETPID:
|
|
case GETNCNT:
|
|
case GETZCNT:
|
|
case SETVAL:
|
|
case SETALL:
|
|
err = semctl_main(ns,semid,semnum,cmd,version,arg);
|
|
return err;
|
|
case IPC_RMID:
|
|
case IPC_SET:
|
|
err = semctl_down(ns, semid, cmd, version, arg);
|
|
return err;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
|
|
asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
|
|
{
|
|
return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
|
|
}
|
|
SYSCALL_ALIAS(sys_semctl, SyS_semctl);
|
|
#endif
|
|
|
|
/* If the task doesn't already have a undo_list, then allocate one
|
|
* here. We guarantee there is only one thread using this undo list,
|
|
* and current is THE ONE
|
|
*
|
|
* If this allocation and assignment succeeds, but later
|
|
* portions of this code fail, there is no need to free the sem_undo_list.
|
|
* Just let it stay associated with the task, and it'll be freed later
|
|
* at exit time.
|
|
*
|
|
* This can block, so callers must hold no locks.
|
|
*/
|
|
static inline int get_undo_list(struct sem_undo_list **undo_listp)
|
|
{
|
|
struct sem_undo_list *undo_list;
|
|
|
|
undo_list = current->sysvsem.undo_list;
|
|
if (!undo_list) {
|
|
undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
|
|
if (undo_list == NULL)
|
|
return -ENOMEM;
|
|
spin_lock_init(&undo_list->lock);
|
|
atomic_set(&undo_list->refcnt, 1);
|
|
INIT_LIST_HEAD(&undo_list->list_proc);
|
|
|
|
current->sysvsem.undo_list = undo_list;
|
|
}
|
|
*undo_listp = undo_list;
|
|
return 0;
|
|
}
|
|
|
|
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
|
|
{
|
|
struct sem_undo *walk;
|
|
|
|
list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) {
|
|
if (walk->semid == semid)
|
|
return walk;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* find_alloc_undo - Lookup (and if not present create) undo array
|
|
* @ns: namespace
|
|
* @semid: semaphore array id
|
|
*
|
|
* The function looks up (and if not present creates) the undo structure.
|
|
* The size of the undo structure depends on the size of the semaphore
|
|
* array, thus the alloc path is not that straightforward.
|
|
* Lifetime-rules: sem_undo is rcu-protected, on success, the function
|
|
* performs a rcu_read_lock().
|
|
*/
|
|
static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
|
|
{
|
|
struct sem_array *sma;
|
|
struct sem_undo_list *ulp;
|
|
struct sem_undo *un, *new;
|
|
int nsems;
|
|
int error;
|
|
|
|
error = get_undo_list(&ulp);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
|
|
rcu_read_lock();
|
|
spin_lock(&ulp->lock);
|
|
un = lookup_undo(ulp, semid);
|
|
spin_unlock(&ulp->lock);
|
|
if (likely(un!=NULL))
|
|
goto out;
|
|
rcu_read_unlock();
|
|
|
|
/* no undo structure around - allocate one. */
|
|
/* step 1: figure out the size of the semaphore array */
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return ERR_PTR(PTR_ERR(sma));
|
|
|
|
nsems = sma->sem_nsems;
|
|
sem_getref_and_unlock(sma);
|
|
|
|
/* step 2: allocate new undo structure */
|
|
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
|
|
if (!new) {
|
|
sem_putref(sma);
|
|
return ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
/* step 3: Acquire the lock on semaphore array */
|
|
sem_lock_and_putref(sma);
|
|
if (sma->sem_perm.deleted) {
|
|
sem_unlock(sma);
|
|
kfree(new);
|
|
un = ERR_PTR(-EIDRM);
|
|
goto out;
|
|
}
|
|
spin_lock(&ulp->lock);
|
|
|
|
/*
|
|
* step 4: check for races: did someone else allocate the undo struct?
|
|
*/
|
|
un = lookup_undo(ulp, semid);
|
|
if (un) {
|
|
kfree(new);
|
|
goto success;
|
|
}
|
|
/* step 5: initialize & link new undo structure */
|
|
new->semadj = (short *) &new[1];
|
|
new->ulp = ulp;
|
|
new->semid = semid;
|
|
assert_spin_locked(&ulp->lock);
|
|
list_add_rcu(&new->list_proc, &ulp->list_proc);
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_add(&new->list_id, &sma->list_id);
|
|
un = new;
|
|
|
|
success:
|
|
spin_unlock(&ulp->lock);
|
|
rcu_read_lock();
|
|
sem_unlock(sma);
|
|
out:
|
|
return un;
|
|
}
|
|
|
|
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|
unsigned, nsops, const struct timespec __user *, timeout)
|
|
{
|
|
int error = -EINVAL;
|
|
struct sem_array *sma;
|
|
struct sembuf fast_sops[SEMOPM_FAST];
|
|
struct sembuf* sops = fast_sops, *sop;
|
|
struct sem_undo *un;
|
|
int undos = 0, alter = 0, max;
|
|
struct sem_queue queue;
|
|
unsigned long jiffies_left = 0;
|
|
struct ipc_namespace *ns;
|
|
|
|
ns = current->nsproxy->ipc_ns;
|
|
|
|
if (nsops < 1 || semid < 0)
|
|
return -EINVAL;
|
|
if (nsops > ns->sc_semopm)
|
|
return -E2BIG;
|
|
if(nsops > SEMOPM_FAST) {
|
|
sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
|
|
if(sops==NULL)
|
|
return -ENOMEM;
|
|
}
|
|
if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
|
|
error=-EFAULT;
|
|
goto out_free;
|
|
}
|
|
if (timeout) {
|
|
struct timespec _timeout;
|
|
if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
|
|
error = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
|
|
_timeout.tv_nsec >= 1000000000L) {
|
|
error = -EINVAL;
|
|
goto out_free;
|
|
}
|
|
jiffies_left = timespec_to_jiffies(&_timeout);
|
|
}
|
|
max = 0;
|
|
for (sop = sops; sop < sops + nsops; sop++) {
|
|
if (sop->sem_num >= max)
|
|
max = sop->sem_num;
|
|
if (sop->sem_flg & SEM_UNDO)
|
|
undos = 1;
|
|
if (sop->sem_op != 0)
|
|
alter = 1;
|
|
}
|
|
|
|
if (undos) {
|
|
un = find_alloc_undo(ns, semid);
|
|
if (IS_ERR(un)) {
|
|
error = PTR_ERR(un);
|
|
goto out_free;
|
|
}
|
|
} else
|
|
un = NULL;
|
|
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
if (un)
|
|
rcu_read_unlock();
|
|
error = PTR_ERR(sma);
|
|
goto out_free;
|
|
}
|
|
|
|
/*
|
|
* semid identifiers are not unique - find_alloc_undo may have
|
|
* allocated an undo structure, it was invalidated by an RMID
|
|
* and now a new array with received the same id. Check and fail.
|
|
* This case can be detected checking un->semid. The existance of
|
|
* "un" itself is guaranteed by rcu.
|
|
*/
|
|
error = -EIDRM;
|
|
if (un) {
|
|
if (un->semid == -1) {
|
|
rcu_read_unlock();
|
|
goto out_unlock_free;
|
|
} else {
|
|
/*
|
|
* rcu lock can be released, "un" cannot disappear:
|
|
* - sem_lock is acquired, thus IPC_RMID is
|
|
* impossible.
|
|
* - exit_sem is impossible, it always operates on
|
|
* current (or a dead task).
|
|
*/
|
|
|
|
rcu_read_unlock();
|
|
}
|
|
}
|
|
|
|
error = -EFBIG;
|
|
if (max >= sma->sem_nsems)
|
|
goto out_unlock_free;
|
|
|
|
error = -EACCES;
|
|
if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
|
|
goto out_unlock_free;
|
|
|
|
error = security_sem_semop(sma, sops, nsops, alter);
|
|
if (error)
|
|
goto out_unlock_free;
|
|
|
|
error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
|
|
if (error <= 0) {
|
|
if (alter && error == 0)
|
|
update_queue (sma);
|
|
goto out_unlock_free;
|
|
}
|
|
|
|
/* We need to sleep on this operation, so we put the current
|
|
* task into the pending queue and go to sleep.
|
|
*/
|
|
|
|
queue.sops = sops;
|
|
queue.nsops = nsops;
|
|
queue.undo = un;
|
|
queue.pid = task_tgid_vnr(current);
|
|
queue.alter = alter;
|
|
if (alter)
|
|
list_add_tail(&queue.list, &sma->sem_pending);
|
|
else
|
|
list_add(&queue.list, &sma->sem_pending);
|
|
|
|
queue.status = -EINTR;
|
|
queue.sleeper = current;
|
|
current->state = TASK_INTERRUPTIBLE;
|
|
sem_unlock(sma);
|
|
|
|
if (timeout)
|
|
jiffies_left = schedule_timeout(jiffies_left);
|
|
else
|
|
schedule();
|
|
|
|
error = queue.status;
|
|
while(unlikely(error == IN_WAKEUP)) {
|
|
cpu_relax();
|
|
error = queue.status;
|
|
}
|
|
|
|
if (error != -EINTR) {
|
|
/* fast path: update_queue already obtained all requested
|
|
* resources */
|
|
goto out_free;
|
|
}
|
|
|
|
sma = sem_lock(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
error = -EIDRM;
|
|
goto out_free;
|
|
}
|
|
|
|
/*
|
|
* If queue.status != -EINTR we are woken up by another process
|
|
*/
|
|
error = queue.status;
|
|
if (error != -EINTR) {
|
|
goto out_unlock_free;
|
|
}
|
|
|
|
/*
|
|
* If an interrupt occurred we have to clean up the queue
|
|
*/
|
|
if (timeout && jiffies_left == 0)
|
|
error = -EAGAIN;
|
|
list_del(&queue.list);
|
|
|
|
out_unlock_free:
|
|
sem_unlock(sma);
|
|
out_free:
|
|
if(sops != fast_sops)
|
|
kfree(sops);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
|
|
unsigned, nsops)
|
|
{
|
|
return sys_semtimedop(semid, tsops, nsops, NULL);
|
|
}
|
|
|
|
/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
|
|
* parent and child tasks.
|
|
*/
|
|
|
|
int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
|
|
{
|
|
struct sem_undo_list *undo_list;
|
|
int error;
|
|
|
|
if (clone_flags & CLONE_SYSVSEM) {
|
|
error = get_undo_list(&undo_list);
|
|
if (error)
|
|
return error;
|
|
atomic_inc(&undo_list->refcnt);
|
|
tsk->sysvsem.undo_list = undo_list;
|
|
} else
|
|
tsk->sysvsem.undo_list = NULL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* add semadj values to semaphores, free undo structures.
|
|
* undo structures are not freed when semaphore arrays are destroyed
|
|
* so some of them may be out of date.
|
|
* IMPLEMENTATION NOTE: There is some confusion over whether the
|
|
* set of adjustments that needs to be done should be done in an atomic
|
|
* manner or not. That is, if we are attempting to decrement the semval
|
|
* should we queue up and wait until we can do so legally?
|
|
* The original implementation attempted to do this (queue and wait).
|
|
* The current implementation does not do so. The POSIX standard
|
|
* and SVID should be consulted to determine what behavior is mandated.
|
|
*/
|
|
void exit_sem(struct task_struct *tsk)
|
|
{
|
|
struct sem_undo_list *ulp;
|
|
|
|
ulp = tsk->sysvsem.undo_list;
|
|
if (!ulp)
|
|
return;
|
|
tsk->sysvsem.undo_list = NULL;
|
|
|
|
if (!atomic_dec_and_test(&ulp->refcnt))
|
|
return;
|
|
|
|
for (;;) {
|
|
struct sem_array *sma;
|
|
struct sem_undo *un;
|
|
int semid;
|
|
int i;
|
|
|
|
rcu_read_lock();
|
|
un = list_entry_rcu(ulp->list_proc.next,
|
|
struct sem_undo, list_proc);
|
|
if (&un->list_proc == &ulp->list_proc)
|
|
semid = -1;
|
|
else
|
|
semid = un->semid;
|
|
rcu_read_unlock();
|
|
|
|
if (semid == -1)
|
|
break;
|
|
|
|
sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
|
|
|
|
/* exit_sem raced with IPC_RMID, nothing to do */
|
|
if (IS_ERR(sma))
|
|
continue;
|
|
|
|
un = lookup_undo(ulp, semid);
|
|
if (un == NULL) {
|
|
/* exit_sem raced with IPC_RMID+semget() that created
|
|
* exactly the same semid. Nothing to do.
|
|
*/
|
|
sem_unlock(sma);
|
|
continue;
|
|
}
|
|
|
|
/* remove un from the linked lists */
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_del(&un->list_id);
|
|
|
|
spin_lock(&ulp->lock);
|
|
list_del_rcu(&un->list_proc);
|
|
spin_unlock(&ulp->lock);
|
|
|
|
/* perform adjustments registered in un */
|
|
for (i = 0; i < sma->sem_nsems; i++) {
|
|
struct sem * semaphore = &sma->sem_base[i];
|
|
if (un->semadj[i]) {
|
|
semaphore->semval += un->semadj[i];
|
|
/*
|
|
* Range checks of the new semaphore value,
|
|
* not defined by sus:
|
|
* - Some unices ignore the undo entirely
|
|
* (e.g. HP UX 11i 11.22, Tru64 V5.1)
|
|
* - some cap the value (e.g. FreeBSD caps
|
|
* at 0, but doesn't enforce SEMVMX)
|
|
*
|
|
* Linux caps the semaphore value, both at 0
|
|
* and at SEMVMX.
|
|
*
|
|
* Manfred <manfred@colorfullife.com>
|
|
*/
|
|
if (semaphore->semval < 0)
|
|
semaphore->semval = 0;
|
|
if (semaphore->semval > SEMVMX)
|
|
semaphore->semval = SEMVMX;
|
|
semaphore->sempid = task_tgid_vnr(current);
|
|
}
|
|
}
|
|
sma->sem_otime = get_seconds();
|
|
/* maybe some queued-up processes were waiting for this */
|
|
update_queue(sma);
|
|
sem_unlock(sma);
|
|
|
|
call_rcu(&un->rcu, free_un);
|
|
}
|
|
kfree(ulp);
|
|
}
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
|
|
{
|
|
struct sem_array *sma = it;
|
|
|
|
return seq_printf(s,
|
|
"%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
|
|
sma->sem_perm.key,
|
|
sma->sem_perm.id,
|
|
sma->sem_perm.mode,
|
|
sma->sem_nsems,
|
|
sma->sem_perm.uid,
|
|
sma->sem_perm.gid,
|
|
sma->sem_perm.cuid,
|
|
sma->sem_perm.cgid,
|
|
sma->sem_otime,
|
|
sma->sem_ctime);
|
|
}
|
|
#endif
|