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sem_ctime is initialized to the semget() time and then updated at every semctl() that changes the array. Thus it does not represent the time of the last change. Especially, semop() calls are only stored in sem_otime, not in sem_ctime. This is already described in ipc/sem.c, I just overlooked that there is a comment in include/linux/sem.h and man semctl(2) as well. So: Correct wrong comments. Link: http://lkml.kernel.org/r/20170515171912.6298-4-manfred@colorfullife.com Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Kees Cook <keescook@chromium.org> Cc: <1vier1@web.de> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Fabian Frederick <fabf@skynet.be> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
#ifndef _LINUX_SEM_H
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#define _LINUX_SEM_H
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#include <linux/atomic.h>
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#include <linux/rcupdate.h>
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#include <linux/cache.h>
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#include <uapi/linux/sem.h>
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struct task_struct;
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/* One semaphore structure for each semaphore in the system. */
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struct sem {
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int semval; /* current value */
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/*
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* PID of the process that last modified the semaphore. For
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* Linux, specifically these are:
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* - semop
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* - semctl, via SETVAL and SETALL.
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* - at task exit when performing undo adjustments (see exit_sem).
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*/
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int sempid;
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spinlock_t lock; /* spinlock for fine-grained semtimedop */
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struct list_head pending_alter; /* pending single-sop operations */
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/* that alter the semaphore */
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struct list_head pending_const; /* pending single-sop operations */
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/* that do not alter the semaphore*/
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time_t sem_otime; /* candidate for sem_otime */
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} ____cacheline_aligned_in_smp;
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/* One sem_array data structure for each set of semaphores in the system. */
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struct sem_array {
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struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */
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time_t sem_ctime; /* create/last semctl() time */
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struct list_head pending_alter; /* pending operations */
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/* that alter the array */
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struct list_head pending_const; /* pending complex operations */
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/* that do not alter semvals */
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struct list_head list_id; /* undo requests on this array */
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int sem_nsems; /* no. of semaphores in array */
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int complex_count; /* pending complex operations */
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unsigned int use_global_lock;/* >0: global lock required */
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struct sem sems[];
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};
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#ifdef CONFIG_SYSVIPC
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struct sysv_sem {
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struct sem_undo_list *undo_list;
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};
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extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
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extern void exit_sem(struct task_struct *tsk);
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#else
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struct sysv_sem {
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/* empty */
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};
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static inline int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
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{
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return 0;
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}
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static inline void exit_sem(struct task_struct *tsk)
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{
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return;
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}
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#endif
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#endif /* _LINUX_SEM_H */
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