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![Peter Zijlstra](/assets/img/avatar_default.png)
Extend lockdep to validate lock wait-type context. The current wait-types are: LD_WAIT_FREE, /* wait free, rcu etc.. */ LD_WAIT_SPIN, /* spin loops, raw_spinlock_t etc.. */ LD_WAIT_CONFIG, /* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */ LD_WAIT_SLEEP, /* sleeping locks, mutex_t etc.. */ Where lockdep validates that the current lock (the one being acquired) fits in the current wait-context (as generated by the held stack). This ensures that there is no attempt to acquire mutexes while holding spinlocks, to acquire spinlocks while holding raw_spinlocks and so on. In other words, its a more fancy might_sleep(). Obviously RCU made the entire ordeal more complex than a simple single value test because RCU can be acquired in (pretty much) any context and while it presents a context to nested locks it is not the same as it got acquired in. Therefore its necessary to split the wait_type into two values, one representing the acquire (outer) and one representing the nested context (inner). For most 'normal' locks these two are the same. [ To make static initialization easier we have the rule that: .outer == INV means .outer == .inner; because INV == 0. ] It further means that its required to find the minimal .inner of the held stack to compare against the outer of the new lock; because while 'normal' RCU presents a CONFIG type to nested locks, if it is taken while already holding a SPIN type it obviously doesn't relax the rules. Below is an example output generated by the trivial test code: raw_spin_lock(&foo); spin_lock(&bar); spin_unlock(&bar); raw_spin_unlock(&foo); [ BUG: Invalid wait context ] ----------------------------- swapper/0/1 is trying to lock: ffffc90000013f20 (&bar){....}-{3:3}, at: kernel_init+0xdb/0x187 other info that might help us debug this: 1 lock held by swapper/0/1: #0: ffffc90000013ee0 (&foo){+.+.}-{2:2}, at: kernel_init+0xd1/0x187 The way to read it is to look at the new -{n,m} part in the lock description; -{3:3} for the attempted lock, and try and match that up to the held locks, which in this case is the one: -{2,2}. This tells that the acquiring lock requires a more relaxed environment than presented by the lock stack. Currently only the normal locks and RCU are converted, the rest of the lockdep users defaults to .inner = INV which is ignored. More conversions can be done when desired. The check for spinlock_t nesting is not enabled by default. It's a separate config option for now as there are known problems which are currently addressed. The config option allows to identify these problems and to verify that the solutions found are indeed solving them. The config switch will be removed and the checks will permanently enabled once the vast majority of issues has been addressed. [ bigeasy: Move LD_WAIT_FREE,… out of CONFIG_LOCKDEP to avoid compile failure with CONFIG_DEBUG_SPINLOCK + !CONFIG_LOCKDEP] [ tglx: Add the config option ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.427089655@linutronix.de
216 lines
6.6 KiB
C
216 lines
6.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Mutexes: blocking mutual exclusion locks
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*
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* started by Ingo Molnar:
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*
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* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* This file contains the main data structure and API definitions.
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*/
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#ifndef __LINUX_MUTEX_H
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#define __LINUX_MUTEX_H
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#include <asm/current.h>
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#include <linux/list.h>
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#include <linux/spinlock_types.h>
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#include <linux/lockdep.h>
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#include <linux/atomic.h>
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#include <asm/processor.h>
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#include <linux/osq_lock.h>
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#include <linux/debug_locks.h>
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struct ww_acquire_ctx;
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/*
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* Simple, straightforward mutexes with strict semantics:
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*
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* - only one task can hold the mutex at a time
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* - only the owner can unlock the mutex
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* - multiple unlocks are not permitted
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* - recursive locking is not permitted
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* - a mutex object must be initialized via the API
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* - a mutex object must not be initialized via memset or copying
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* - task may not exit with mutex held
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* - memory areas where held locks reside must not be freed
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* - held mutexes must not be reinitialized
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* - mutexes may not be used in hardware or software interrupt
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* contexts such as tasklets and timers
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*
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* These semantics are fully enforced when DEBUG_MUTEXES is
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* enabled. Furthermore, besides enforcing the above rules, the mutex
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* debugging code also implements a number of additional features
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* that make lock debugging easier and faster:
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*
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* - uses symbolic names of mutexes, whenever they are printed in debug output
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* - point-of-acquire tracking, symbolic lookup of function names
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* - list of all locks held in the system, printout of them
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* - owner tracking
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* - detects self-recursing locks and prints out all relevant info
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* - detects multi-task circular deadlocks and prints out all affected
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* locks and tasks (and only those tasks)
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*/
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struct mutex {
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atomic_long_t owner;
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spinlock_t wait_lock;
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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struct optimistic_spin_queue osq; /* Spinner MCS lock */
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#endif
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struct list_head wait_list;
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#ifdef CONFIG_DEBUG_MUTEXES
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void *magic;
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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};
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/*
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* This is the control structure for tasks blocked on mutex,
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* which resides on the blocked task's kernel stack:
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*/
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struct mutex_waiter {
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struct list_head list;
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struct task_struct *task;
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struct ww_acquire_ctx *ww_ctx;
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#ifdef CONFIG_DEBUG_MUTEXES
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void *magic;
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#endif
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};
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#ifdef CONFIG_DEBUG_MUTEXES
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#define __DEBUG_MUTEX_INITIALIZER(lockname) \
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, .magic = &lockname
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extern void mutex_destroy(struct mutex *lock);
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#else
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# define __DEBUG_MUTEX_INITIALIZER(lockname)
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static inline void mutex_destroy(struct mutex *lock) {}
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#endif
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/**
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* mutex_init - initialize the mutex
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* @mutex: the mutex to be initialized
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*
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* Initialize the mutex to unlocked state.
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*
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* It is not allowed to initialize an already locked mutex.
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*/
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#define mutex_init(mutex) \
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do { \
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static struct lock_class_key __key; \
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\
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__mutex_init((mutex), #mutex, &__key); \
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} while (0)
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
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, .dep_map = { \
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.name = #lockname, \
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.wait_type_inner = LD_WAIT_SLEEP, \
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}
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#else
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# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
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#endif
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#define __MUTEX_INITIALIZER(lockname) \
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{ .owner = ATOMIC_LONG_INIT(0) \
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, .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
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, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
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__DEBUG_MUTEX_INITIALIZER(lockname) \
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__DEP_MAP_MUTEX_INITIALIZER(lockname) }
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#define DEFINE_MUTEX(mutexname) \
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struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
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extern void __mutex_init(struct mutex *lock, const char *name,
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struct lock_class_key *key);
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/**
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* mutex_is_locked - is the mutex locked
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* @lock: the mutex to be queried
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*
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* Returns true if the mutex is locked, false if unlocked.
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*/
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extern bool mutex_is_locked(struct mutex *lock);
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/*
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* See kernel/locking/mutex.c for detailed documentation of these APIs.
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* Also see Documentation/locking/mutex-design.rst.
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*/
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
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extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
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extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
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unsigned int subclass);
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extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
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unsigned int subclass);
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extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass);
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#define mutex_lock(lock) mutex_lock_nested(lock, 0)
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#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
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#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
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#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
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#define mutex_lock_nest_lock(lock, nest_lock) \
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do { \
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typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
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_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
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} while (0)
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#else
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extern void mutex_lock(struct mutex *lock);
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extern int __must_check mutex_lock_interruptible(struct mutex *lock);
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extern int __must_check mutex_lock_killable(struct mutex *lock);
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extern void mutex_lock_io(struct mutex *lock);
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# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
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# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
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# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
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# define mutex_lock_nest_lock(lock, nest_lock) mutex_lock(lock)
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# define mutex_lock_io_nested(lock, subclass) mutex_lock(lock)
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#endif
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/*
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* NOTE: mutex_trylock() follows the spin_trylock() convention,
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* not the down_trylock() convention!
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*
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* Returns 1 if the mutex has been acquired successfully, and 0 on contention.
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*/
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extern int mutex_trylock(struct mutex *lock);
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extern void mutex_unlock(struct mutex *lock);
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extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
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/*
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* These values are chosen such that FAIL and SUCCESS match the
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* values of the regular mutex_trylock().
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*/
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enum mutex_trylock_recursive_enum {
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MUTEX_TRYLOCK_FAILED = 0,
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MUTEX_TRYLOCK_SUCCESS = 1,
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MUTEX_TRYLOCK_RECURSIVE,
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};
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/**
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* mutex_trylock_recursive - trylock variant that allows recursive locking
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* @lock: mutex to be locked
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*
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* This function should not be used, _ever_. It is purely for hysterical GEM
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* raisins, and once those are gone this will be removed.
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*
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* Returns:
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* - MUTEX_TRYLOCK_FAILED - trylock failed,
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* - MUTEX_TRYLOCK_SUCCESS - lock acquired,
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* - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
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*/
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extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
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mutex_trylock_recursive(struct mutex *lock);
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#endif /* __LINUX_MUTEX_H */
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