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1460cb65a1
We sometimes end up propagating IO blocking through mutexes; however, because there currently is no way of annotating mutex sleeps as iowait, there are cases where iowait and /proc/stat:procs_blocked report misleading numbers obscuring the actual state of the system. This patch adds mutex_lock_io() so that mutex sleeps can be marked as iowait in those cases. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: adilger.kernel@dilger.ca Cc: jack@suse.com Cc: kernel-team@fb.com Cc: mingbo@fb.com Cc: tytso@mit.edu Link: http://lkml.kernel.org/r/1477673892-28940-4-git-send-email-tj@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
1094 lines
28 KiB
C
1094 lines
28 KiB
C
/*
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* kernel/locking/mutex.c
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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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* Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
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* David Howells for suggestions and improvements.
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*
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* - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
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* from the -rt tree, where it was originally implemented for rtmutexes
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* by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
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* and Sven Dietrich.
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*
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* Also see Documentation/locking/mutex-design.txt.
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*/
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#include <linux/mutex.h>
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#include <linux/ww_mutex.h>
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#include <linux/sched.h>
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#include <linux/sched/rt.h>
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#include <linux/export.h>
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#include <linux/spinlock.h>
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#include <linux/interrupt.h>
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#include <linux/debug_locks.h>
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#include <linux/osq_lock.h>
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#ifdef CONFIG_DEBUG_MUTEXES
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# include "mutex-debug.h"
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#else
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# include "mutex.h"
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#endif
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void
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__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
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{
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atomic_long_set(&lock->owner, 0);
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spin_lock_init(&lock->wait_lock);
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INIT_LIST_HEAD(&lock->wait_list);
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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osq_lock_init(&lock->osq);
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#endif
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debug_mutex_init(lock, name, key);
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}
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EXPORT_SYMBOL(__mutex_init);
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/*
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* @owner: contains: 'struct task_struct *' to the current lock owner,
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* NULL means not owned. Since task_struct pointers are aligned at
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* ARCH_MIN_TASKALIGN (which is at least sizeof(void *)), we have low
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* bits to store extra state.
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*
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* Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
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* Bit1 indicates unlock needs to hand the lock to the top-waiter
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*/
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#define MUTEX_FLAG_WAITERS 0x01
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#define MUTEX_FLAG_HANDOFF 0x02
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#define MUTEX_FLAGS 0x03
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static inline struct task_struct *__owner_task(unsigned long owner)
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{
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return (struct task_struct *)(owner & ~MUTEX_FLAGS);
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}
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static inline unsigned long __owner_flags(unsigned long owner)
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{
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return owner & MUTEX_FLAGS;
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}
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/*
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* Actual trylock that will work on any unlocked state.
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*
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* When setting the owner field, we must preserve the low flag bits.
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*
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* Be careful with @handoff, only set that in a wait-loop (where you set
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* HANDOFF) to avoid recursive lock attempts.
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*/
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static inline bool __mutex_trylock(struct mutex *lock, const bool handoff)
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{
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unsigned long owner, curr = (unsigned long)current;
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owner = atomic_long_read(&lock->owner);
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for (;;) { /* must loop, can race against a flag */
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unsigned long old, flags = __owner_flags(owner);
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if (__owner_task(owner)) {
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if (handoff && unlikely(__owner_task(owner) == current)) {
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/*
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* Provide ACQUIRE semantics for the lock-handoff.
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*
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* We cannot easily use load-acquire here, since
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* the actual load is a failed cmpxchg, which
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* doesn't imply any barriers.
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*
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* Also, this is a fairly unlikely scenario, and
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* this contains the cost.
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*/
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smp_mb(); /* ACQUIRE */
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return true;
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}
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return false;
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}
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/*
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* We set the HANDOFF bit, we must make sure it doesn't live
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* past the point where we acquire it. This would be possible
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* if we (accidentally) set the bit on an unlocked mutex.
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*/
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if (handoff)
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flags &= ~MUTEX_FLAG_HANDOFF;
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old = atomic_long_cmpxchg_acquire(&lock->owner, owner, curr | flags);
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if (old == owner)
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return true;
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owner = old;
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}
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}
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#ifndef CONFIG_DEBUG_LOCK_ALLOC
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/*
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* Lockdep annotations are contained to the slow paths for simplicity.
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* There is nothing that would stop spreading the lockdep annotations outwards
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* except more code.
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*/
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/*
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* Optimistic trylock that only works in the uncontended case. Make sure to
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* follow with a __mutex_trylock() before failing.
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*/
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static __always_inline bool __mutex_trylock_fast(struct mutex *lock)
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{
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unsigned long curr = (unsigned long)current;
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if (!atomic_long_cmpxchg_acquire(&lock->owner, 0UL, curr))
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return true;
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return false;
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}
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static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
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{
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unsigned long curr = (unsigned long)current;
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if (atomic_long_cmpxchg_release(&lock->owner, curr, 0UL) == curr)
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return true;
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return false;
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}
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#endif
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static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
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{
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atomic_long_or(flag, &lock->owner);
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}
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static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag)
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{
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atomic_long_andnot(flag, &lock->owner);
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}
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static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter)
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{
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return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;
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}
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/*
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* Give up ownership to a specific task, when @task = NULL, this is equivalent
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* to a regular unlock. Clears HANDOFF, preserves WAITERS. Provides RELEASE
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* semantics like a regular unlock, the __mutex_trylock() provides matching
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* ACQUIRE semantics for the handoff.
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*/
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static void __mutex_handoff(struct mutex *lock, struct task_struct *task)
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{
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unsigned long owner = atomic_long_read(&lock->owner);
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for (;;) {
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unsigned long old, new;
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#ifdef CONFIG_DEBUG_MUTEXES
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DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
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#endif
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new = (owner & MUTEX_FLAG_WAITERS);
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new |= (unsigned long)task;
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old = atomic_long_cmpxchg_release(&lock->owner, owner, new);
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if (old == owner)
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break;
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owner = old;
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}
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}
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#ifndef CONFIG_DEBUG_LOCK_ALLOC
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/*
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* We split the mutex lock/unlock logic into separate fastpath and
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* slowpath functions, to reduce the register pressure on the fastpath.
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* We also put the fastpath first in the kernel image, to make sure the
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* branch is predicted by the CPU as default-untaken.
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*/
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static void __sched __mutex_lock_slowpath(struct mutex *lock);
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/**
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* mutex_lock - acquire the mutex
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* @lock: the mutex to be acquired
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*
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* Lock the mutex exclusively for this task. If the mutex is not
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* available right now, it will sleep until it can get it.
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*
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* The mutex must later on be released by the same task that
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* acquired it. Recursive locking is not allowed. The task
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* may not exit without first unlocking the mutex. Also, kernel
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* memory where the mutex resides must not be freed with
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* the mutex still locked. The mutex must first be initialized
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* (or statically defined) before it can be locked. memset()-ing
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* the mutex to 0 is not allowed.
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*
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* ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
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* checks that will enforce the restrictions and will also do
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* deadlock debugging. )
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*
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* This function is similar to (but not equivalent to) down().
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*/
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void __sched mutex_lock(struct mutex *lock)
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{
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might_sleep();
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if (!__mutex_trylock_fast(lock))
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__mutex_lock_slowpath(lock);
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}
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EXPORT_SYMBOL(mutex_lock);
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#endif
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static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
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struct ww_acquire_ctx *ww_ctx)
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{
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#ifdef CONFIG_DEBUG_MUTEXES
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/*
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* If this WARN_ON triggers, you used ww_mutex_lock to acquire,
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* but released with a normal mutex_unlock in this call.
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*
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* This should never happen, always use ww_mutex_unlock.
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*/
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DEBUG_LOCKS_WARN_ON(ww->ctx);
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/*
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* Not quite done after calling ww_acquire_done() ?
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
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if (ww_ctx->contending_lock) {
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/*
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* After -EDEADLK you tried to
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* acquire a different ww_mutex? Bad!
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
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/*
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* You called ww_mutex_lock after receiving -EDEADLK,
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* but 'forgot' to unlock everything else first?
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
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ww_ctx->contending_lock = NULL;
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}
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/*
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* Naughty, using a different class will lead to undefined behavior!
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
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#endif
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ww_ctx->acquired++;
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}
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/*
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* After acquiring lock with fastpath or when we lost out in contested
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* slowpath, set ctx and wake up any waiters so they can recheck.
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*/
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static __always_inline void
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ww_mutex_set_context_fastpath(struct ww_mutex *lock,
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struct ww_acquire_ctx *ctx)
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{
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unsigned long flags;
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struct mutex_waiter *cur;
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ww_mutex_lock_acquired(lock, ctx);
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lock->ctx = ctx;
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/*
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* The lock->ctx update should be visible on all cores before
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* the atomic read is done, otherwise contended waiters might be
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* missed. The contended waiters will either see ww_ctx == NULL
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* and keep spinning, or it will acquire wait_lock, add itself
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* to waiter list and sleep.
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*/
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smp_mb(); /* ^^^ */
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/*
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* Check if lock is contended, if not there is nobody to wake up
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*/
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if (likely(!(atomic_long_read(&lock->base.owner) & MUTEX_FLAG_WAITERS)))
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return;
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/*
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* Uh oh, we raced in fastpath, wake up everyone in this case,
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* so they can see the new lock->ctx.
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*/
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spin_lock_mutex(&lock->base.wait_lock, flags);
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list_for_each_entry(cur, &lock->base.wait_list, list) {
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debug_mutex_wake_waiter(&lock->base, cur);
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wake_up_process(cur->task);
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}
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spin_unlock_mutex(&lock->base.wait_lock, flags);
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}
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/*
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* After acquiring lock in the slowpath set ctx and wake up any
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* waiters so they can recheck.
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*
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* Callers must hold the mutex wait_lock.
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*/
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static __always_inline void
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ww_mutex_set_context_slowpath(struct ww_mutex *lock,
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struct ww_acquire_ctx *ctx)
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{
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struct mutex_waiter *cur;
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ww_mutex_lock_acquired(lock, ctx);
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lock->ctx = ctx;
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/*
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* Give any possible sleeping processes the chance to wake up,
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* so they can recheck if they have to back off.
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*/
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list_for_each_entry(cur, &lock->base.wait_list, list) {
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debug_mutex_wake_waiter(&lock->base, cur);
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wake_up_process(cur->task);
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}
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}
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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/*
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* Look out! "owner" is an entirely speculative pointer
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* access and not reliable.
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*/
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static noinline
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bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
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{
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bool ret = true;
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rcu_read_lock();
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while (__mutex_owner(lock) == owner) {
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/*
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* Ensure we emit the owner->on_cpu, dereference _after_
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* checking lock->owner still matches owner. If that fails,
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* owner might point to freed memory. If it still matches,
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* the rcu_read_lock() ensures the memory stays valid.
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*/
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barrier();
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/*
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* Use vcpu_is_preempted to detect lock holder preemption issue.
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*/
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if (!owner->on_cpu || need_resched() ||
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vcpu_is_preempted(task_cpu(owner))) {
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ret = false;
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break;
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}
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cpu_relax();
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}
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rcu_read_unlock();
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return ret;
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}
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/*
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* Initial check for entering the mutex spinning loop
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*/
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static inline int mutex_can_spin_on_owner(struct mutex *lock)
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{
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struct task_struct *owner;
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int retval = 1;
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if (need_resched())
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return 0;
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rcu_read_lock();
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owner = __mutex_owner(lock);
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/*
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* As lock holder preemption issue, we both skip spinning if task is not
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* on cpu or its cpu is preempted
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*/
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if (owner)
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retval = owner->on_cpu && !vcpu_is_preempted(task_cpu(owner));
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rcu_read_unlock();
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/*
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* If lock->owner is not set, the mutex has been released. Return true
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* such that we'll trylock in the spin path, which is a faster option
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* than the blocking slow path.
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*/
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return retval;
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}
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/*
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* Optimistic spinning.
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*
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* We try to spin for acquisition when we find that the lock owner
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* is currently running on a (different) CPU and while we don't
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* need to reschedule. The rationale is that if the lock owner is
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* running, it is likely to release the lock soon.
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*
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* The mutex spinners are queued up using MCS lock so that only one
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* spinner can compete for the mutex. However, if mutex spinning isn't
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* going to happen, there is no point in going through the lock/unlock
|
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* overhead.
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*
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* Returns true when the lock was taken, otherwise false, indicating
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* that we need to jump to the slowpath and sleep.
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*
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* The waiter flag is set to true if the spinner is a waiter in the wait
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* queue. The waiter-spinner will spin on the lock directly and concurrently
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* with the spinner at the head of the OSQ, if present, until the owner is
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* changed to itself.
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*/
|
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static bool mutex_optimistic_spin(struct mutex *lock,
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struct ww_acquire_ctx *ww_ctx,
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const bool use_ww_ctx, const bool waiter)
|
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{
|
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struct task_struct *task = current;
|
|
|
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if (!waiter) {
|
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/*
|
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* The purpose of the mutex_can_spin_on_owner() function is
|
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* to eliminate the overhead of osq_lock() and osq_unlock()
|
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* in case spinning isn't possible. As a waiter-spinner
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* is not going to take OSQ lock anyway, there is no need
|
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* to call mutex_can_spin_on_owner().
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*/
|
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if (!mutex_can_spin_on_owner(lock))
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goto fail;
|
|
|
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/*
|
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* In order to avoid a stampede of mutex spinners trying to
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* acquire the mutex all at once, the spinners need to take a
|
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* MCS (queued) lock first before spinning on the owner field.
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*/
|
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if (!osq_lock(&lock->osq))
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goto fail;
|
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}
|
|
|
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for (;;) {
|
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struct task_struct *owner;
|
|
|
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if (use_ww_ctx && ww_ctx->acquired > 0) {
|
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struct ww_mutex *ww;
|
|
|
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ww = container_of(lock, struct ww_mutex, base);
|
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/*
|
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* If ww->ctx is set the contents are undefined, only
|
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* by acquiring wait_lock there is a guarantee that
|
|
* they are not invalid when reading.
|
|
*
|
|
* As such, when deadlock detection needs to be
|
|
* performed the optimistic spinning cannot be done.
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*/
|
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if (READ_ONCE(ww->ctx))
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goto fail_unlock;
|
|
}
|
|
|
|
/*
|
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* If there's an owner, wait for it to either
|
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* release the lock or go to sleep.
|
|
*/
|
|
owner = __mutex_owner(lock);
|
|
if (owner) {
|
|
if (waiter && owner == task) {
|
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smp_mb(); /* ACQUIRE */
|
|
break;
|
|
}
|
|
|
|
if (!mutex_spin_on_owner(lock, owner))
|
|
goto fail_unlock;
|
|
}
|
|
|
|
/* Try to acquire the mutex if it is unlocked. */
|
|
if (__mutex_trylock(lock, waiter))
|
|
break;
|
|
|
|
/*
|
|
* The cpu_relax() call is a compiler barrier which forces
|
|
* everything in this loop to be re-loaded. We don't need
|
|
* memory barriers as we'll eventually observe the right
|
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* values at the cost of a few extra spins.
|
|
*/
|
|
cpu_relax();
|
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}
|
|
|
|
if (!waiter)
|
|
osq_unlock(&lock->osq);
|
|
|
|
return true;
|
|
|
|
|
|
fail_unlock:
|
|
if (!waiter)
|
|
osq_unlock(&lock->osq);
|
|
|
|
fail:
|
|
/*
|
|
* If we fell out of the spin path because of need_resched(),
|
|
* reschedule now, before we try-lock the mutex. This avoids getting
|
|
* scheduled out right after we obtained the mutex.
|
|
*/
|
|
if (need_resched()) {
|
|
/*
|
|
* We _should_ have TASK_RUNNING here, but just in case
|
|
* we do not, make it so, otherwise we might get stuck.
|
|
*/
|
|
__set_current_state(TASK_RUNNING);
|
|
schedule_preempt_disabled();
|
|
}
|
|
|
|
return false;
|
|
}
|
|
#else
|
|
static bool mutex_optimistic_spin(struct mutex *lock,
|
|
struct ww_acquire_ctx *ww_ctx,
|
|
const bool use_ww_ctx, const bool waiter)
|
|
{
|
|
return false;
|
|
}
|
|
#endif
|
|
|
|
static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip);
|
|
|
|
/**
|
|
* mutex_unlock - release the mutex
|
|
* @lock: the mutex to be released
|
|
*
|
|
* Unlock a mutex that has been locked by this task previously.
|
|
*
|
|
* This function must not be used in interrupt context. Unlocking
|
|
* of a not locked mutex is not allowed.
|
|
*
|
|
* This function is similar to (but not equivalent to) up().
|
|
*/
|
|
void __sched mutex_unlock(struct mutex *lock)
|
|
{
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
if (__mutex_unlock_fast(lock))
|
|
return;
|
|
#endif
|
|
__mutex_unlock_slowpath(lock, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL(mutex_unlock);
|
|
|
|
/**
|
|
* ww_mutex_unlock - release the w/w mutex
|
|
* @lock: the mutex to be released
|
|
*
|
|
* Unlock a mutex that has been locked by this task previously with any of the
|
|
* ww_mutex_lock* functions (with or without an acquire context). It is
|
|
* forbidden to release the locks after releasing the acquire context.
|
|
*
|
|
* This function must not be used in interrupt context. Unlocking
|
|
* of a unlocked mutex is not allowed.
|
|
*/
|
|
void __sched ww_mutex_unlock(struct ww_mutex *lock)
|
|
{
|
|
/*
|
|
* The unlocking fastpath is the 0->1 transition from 'locked'
|
|
* into 'unlocked' state:
|
|
*/
|
|
if (lock->ctx) {
|
|
#ifdef CONFIG_DEBUG_MUTEXES
|
|
DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
|
|
#endif
|
|
if (lock->ctx->acquired > 0)
|
|
lock->ctx->acquired--;
|
|
lock->ctx = NULL;
|
|
}
|
|
|
|
mutex_unlock(&lock->base);
|
|
}
|
|
EXPORT_SYMBOL(ww_mutex_unlock);
|
|
|
|
static inline int __sched
|
|
__ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
|
|
struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
|
|
|
|
if (!hold_ctx)
|
|
return 0;
|
|
|
|
if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
|
|
(ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
|
|
#ifdef CONFIG_DEBUG_MUTEXES
|
|
DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
|
|
ctx->contending_lock = ww;
|
|
#endif
|
|
return -EDEADLK;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Lock a mutex (possibly interruptible), slowpath:
|
|
*/
|
|
static __always_inline int __sched
|
|
__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
|
|
struct lockdep_map *nest_lock, unsigned long ip,
|
|
struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
|
|
{
|
|
struct task_struct *task = current;
|
|
struct mutex_waiter waiter;
|
|
unsigned long flags;
|
|
bool first = false;
|
|
struct ww_mutex *ww;
|
|
int ret;
|
|
|
|
if (use_ww_ctx) {
|
|
ww = container_of(lock, struct ww_mutex, base);
|
|
if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
|
|
return -EALREADY;
|
|
}
|
|
|
|
preempt_disable();
|
|
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
|
|
|
|
if (__mutex_trylock(lock, false) ||
|
|
mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, false)) {
|
|
/* got the lock, yay! */
|
|
lock_acquired(&lock->dep_map, ip);
|
|
if (use_ww_ctx)
|
|
ww_mutex_set_context_fastpath(ww, ww_ctx);
|
|
preempt_enable();
|
|
return 0;
|
|
}
|
|
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
/*
|
|
* After waiting to acquire the wait_lock, try again.
|
|
*/
|
|
if (__mutex_trylock(lock, false))
|
|
goto skip_wait;
|
|
|
|
debug_mutex_lock_common(lock, &waiter);
|
|
debug_mutex_add_waiter(lock, &waiter, task);
|
|
|
|
/* add waiting tasks to the end of the waitqueue (FIFO): */
|
|
list_add_tail(&waiter.list, &lock->wait_list);
|
|
waiter.task = task;
|
|
|
|
if (__mutex_waiter_is_first(lock, &waiter))
|
|
__mutex_set_flag(lock, MUTEX_FLAG_WAITERS);
|
|
|
|
lock_contended(&lock->dep_map, ip);
|
|
|
|
set_task_state(task, state);
|
|
for (;;) {
|
|
/*
|
|
* Once we hold wait_lock, we're serialized against
|
|
* mutex_unlock() handing the lock off to us, do a trylock
|
|
* before testing the error conditions to make sure we pick up
|
|
* the handoff.
|
|
*/
|
|
if (__mutex_trylock(lock, first))
|
|
goto acquired;
|
|
|
|
/*
|
|
* Check for signals and wound conditions while holding
|
|
* wait_lock. This ensures the lock cancellation is ordered
|
|
* against mutex_unlock() and wake-ups do not go missing.
|
|
*/
|
|
if (unlikely(signal_pending_state(state, task))) {
|
|
ret = -EINTR;
|
|
goto err;
|
|
}
|
|
|
|
if (use_ww_ctx && ww_ctx->acquired > 0) {
|
|
ret = __ww_mutex_lock_check_stamp(lock, ww_ctx);
|
|
if (ret)
|
|
goto err;
|
|
}
|
|
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
schedule_preempt_disabled();
|
|
|
|
if (!first && __mutex_waiter_is_first(lock, &waiter)) {
|
|
first = true;
|
|
__mutex_set_flag(lock, MUTEX_FLAG_HANDOFF);
|
|
}
|
|
|
|
set_task_state(task, state);
|
|
/*
|
|
* Here we order against unlock; we must either see it change
|
|
* state back to RUNNING and fall through the next schedule(),
|
|
* or we must see its unlock and acquire.
|
|
*/
|
|
if ((first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, true)) ||
|
|
__mutex_trylock(lock, first))
|
|
break;
|
|
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
}
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
acquired:
|
|
__set_task_state(task, TASK_RUNNING);
|
|
|
|
mutex_remove_waiter(lock, &waiter, task);
|
|
if (likely(list_empty(&lock->wait_list)))
|
|
__mutex_clear_flag(lock, MUTEX_FLAGS);
|
|
|
|
debug_mutex_free_waiter(&waiter);
|
|
|
|
skip_wait:
|
|
/* got the lock - cleanup and rejoice! */
|
|
lock_acquired(&lock->dep_map, ip);
|
|
|
|
if (use_ww_ctx)
|
|
ww_mutex_set_context_slowpath(ww, ww_ctx);
|
|
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
preempt_enable();
|
|
return 0;
|
|
|
|
err:
|
|
__set_task_state(task, TASK_RUNNING);
|
|
mutex_remove_waiter(lock, &waiter, task);
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
debug_mutex_free_waiter(&waiter);
|
|
mutex_release(&lock->dep_map, 1, ip);
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
void __sched
|
|
mutex_lock_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
might_sleep();
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
|
|
subclass, NULL, _RET_IP_, NULL, 0);
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(mutex_lock_nested);
|
|
|
|
void __sched
|
|
_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
|
|
{
|
|
might_sleep();
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
|
|
0, nest, _RET_IP_, NULL, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
|
|
|
|
int __sched
|
|
mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
might_sleep();
|
|
return __mutex_lock_common(lock, TASK_KILLABLE,
|
|
subclass, NULL, _RET_IP_, NULL, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
|
|
|
|
int __sched
|
|
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
might_sleep();
|
|
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
|
|
subclass, NULL, _RET_IP_, NULL, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
|
|
|
|
void __sched
|
|
mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
int token;
|
|
|
|
might_sleep();
|
|
|
|
token = io_schedule_prepare();
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
|
|
subclass, NULL, _RET_IP_, NULL, 0);
|
|
io_schedule_finish(token);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_io_nested);
|
|
|
|
static inline int
|
|
ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
|
|
unsigned tmp;
|
|
|
|
if (ctx->deadlock_inject_countdown-- == 0) {
|
|
tmp = ctx->deadlock_inject_interval;
|
|
if (tmp > UINT_MAX/4)
|
|
tmp = UINT_MAX;
|
|
else
|
|
tmp = tmp*2 + tmp + tmp/2;
|
|
|
|
ctx->deadlock_inject_interval = tmp;
|
|
ctx->deadlock_inject_countdown = tmp;
|
|
ctx->contending_lock = lock;
|
|
|
|
ww_mutex_unlock(lock);
|
|
|
|
return -EDEADLK;
|
|
}
|
|
#endif
|
|
|
|
return 0;
|
|
}
|
|
|
|
int __sched
|
|
__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
|
|
0, &ctx->dep_map, _RET_IP_, ctx, 1);
|
|
if (!ret && ctx->acquired > 1)
|
|
return ww_mutex_deadlock_injection(lock, ctx);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__ww_mutex_lock);
|
|
|
|
int __sched
|
|
__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
|
|
0, &ctx->dep_map, _RET_IP_, ctx, 1);
|
|
|
|
if (!ret && ctx->acquired > 1)
|
|
return ww_mutex_deadlock_injection(lock, ctx);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Release the lock, slowpath:
|
|
*/
|
|
static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip)
|
|
{
|
|
struct task_struct *next = NULL;
|
|
unsigned long owner, flags;
|
|
DEFINE_WAKE_Q(wake_q);
|
|
|
|
mutex_release(&lock->dep_map, 1, ip);
|
|
|
|
/*
|
|
* Release the lock before (potentially) taking the spinlock such that
|
|
* other contenders can get on with things ASAP.
|
|
*
|
|
* Except when HANDOFF, in that case we must not clear the owner field,
|
|
* but instead set it to the top waiter.
|
|
*/
|
|
owner = atomic_long_read(&lock->owner);
|
|
for (;;) {
|
|
unsigned long old;
|
|
|
|
#ifdef CONFIG_DEBUG_MUTEXES
|
|
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current);
|
|
#endif
|
|
|
|
if (owner & MUTEX_FLAG_HANDOFF)
|
|
break;
|
|
|
|
old = atomic_long_cmpxchg_release(&lock->owner, owner,
|
|
__owner_flags(owner));
|
|
if (old == owner) {
|
|
if (owner & MUTEX_FLAG_WAITERS)
|
|
break;
|
|
|
|
return;
|
|
}
|
|
|
|
owner = old;
|
|
}
|
|
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
debug_mutex_unlock(lock);
|
|
if (!list_empty(&lock->wait_list)) {
|
|
/* get the first entry from the wait-list: */
|
|
struct mutex_waiter *waiter =
|
|
list_first_entry(&lock->wait_list,
|
|
struct mutex_waiter, list);
|
|
|
|
next = waiter->task;
|
|
|
|
debug_mutex_wake_waiter(lock, waiter);
|
|
wake_q_add(&wake_q, next);
|
|
}
|
|
|
|
if (owner & MUTEX_FLAG_HANDOFF)
|
|
__mutex_handoff(lock, next);
|
|
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
|
|
wake_up_q(&wake_q);
|
|
}
|
|
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
/*
|
|
* Here come the less common (and hence less performance-critical) APIs:
|
|
* mutex_lock_interruptible() and mutex_trylock().
|
|
*/
|
|
static noinline int __sched
|
|
__mutex_lock_killable_slowpath(struct mutex *lock);
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_interruptible_slowpath(struct mutex *lock);
|
|
|
|
/**
|
|
* mutex_lock_interruptible - acquire the mutex, interruptible
|
|
* @lock: the mutex to be acquired
|
|
*
|
|
* Lock the mutex like mutex_lock(), and return 0 if the mutex has
|
|
* been acquired or sleep until the mutex becomes available. If a
|
|
* signal arrives while waiting for the lock then this function
|
|
* returns -EINTR.
|
|
*
|
|
* This function is similar to (but not equivalent to) down_interruptible().
|
|
*/
|
|
int __sched mutex_lock_interruptible(struct mutex *lock)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(lock))
|
|
return 0;
|
|
|
|
return __mutex_lock_interruptible_slowpath(lock);
|
|
}
|
|
|
|
EXPORT_SYMBOL(mutex_lock_interruptible);
|
|
|
|
int __sched mutex_lock_killable(struct mutex *lock)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(lock))
|
|
return 0;
|
|
|
|
return __mutex_lock_killable_slowpath(lock);
|
|
}
|
|
EXPORT_SYMBOL(mutex_lock_killable);
|
|
|
|
void __sched mutex_lock_io(struct mutex *lock)
|
|
{
|
|
int token;
|
|
|
|
token = io_schedule_prepare();
|
|
mutex_lock(lock);
|
|
io_schedule_finish(token);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_io);
|
|
|
|
static noinline void __sched
|
|
__mutex_lock_slowpath(struct mutex *lock)
|
|
{
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, NULL, 0);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_killable_slowpath(struct mutex *lock)
|
|
{
|
|
return __mutex_lock_common(lock, TASK_KILLABLE, 0,
|
|
NULL, _RET_IP_, NULL, 0);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_interruptible_slowpath(struct mutex *lock)
|
|
{
|
|
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, NULL, 0);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, ctx, 1);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
|
|
struct ww_acquire_ctx *ctx)
|
|
{
|
|
return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, ctx, 1);
|
|
}
|
|
|
|
#endif
|
|
|
|
/**
|
|
* mutex_trylock - try to acquire the mutex, without waiting
|
|
* @lock: the mutex to be acquired
|
|
*
|
|
* Try to acquire the mutex atomically. Returns 1 if the mutex
|
|
* has been acquired successfully, and 0 on contention.
|
|
*
|
|
* NOTE: this function follows the spin_trylock() convention, so
|
|
* it is negated from the down_trylock() return values! Be careful
|
|
* about this when converting semaphore users to mutexes.
|
|
*
|
|
* This function must not be used in interrupt context. The
|
|
* mutex must be released by the same task that acquired it.
|
|
*/
|
|
int __sched mutex_trylock(struct mutex *lock)
|
|
{
|
|
bool locked = __mutex_trylock(lock, false);
|
|
|
|
if (locked)
|
|
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
|
|
|
|
return locked;
|
|
}
|
|
EXPORT_SYMBOL(mutex_trylock);
|
|
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
int __sched
|
|
__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(&lock->base)) {
|
|
ww_mutex_set_context_fastpath(lock, ctx);
|
|
return 0;
|
|
}
|
|
|
|
return __ww_mutex_lock_slowpath(lock, ctx);
|
|
}
|
|
EXPORT_SYMBOL(__ww_mutex_lock);
|
|
|
|
int __sched
|
|
__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(&lock->base)) {
|
|
ww_mutex_set_context_fastpath(lock, ctx);
|
|
return 0;
|
|
}
|
|
|
|
return __ww_mutex_lock_interruptible_slowpath(lock, ctx);
|
|
}
|
|
EXPORT_SYMBOL(__ww_mutex_lock_interruptible);
|
|
|
|
#endif
|
|
|
|
/**
|
|
* atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
|
|
* @cnt: the atomic which we are to dec
|
|
* @lock: the mutex to return holding if we dec to 0
|
|
*
|
|
* return true and hold lock if we dec to 0, return false otherwise
|
|
*/
|
|
int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
|
|
{
|
|
/* dec if we can't possibly hit 0 */
|
|
if (atomic_add_unless(cnt, -1, 1))
|
|
return 0;
|
|
/* we might hit 0, so take the lock */
|
|
mutex_lock(lock);
|
|
if (!atomic_dec_and_test(cnt)) {
|
|
/* when we actually did the dec, we didn't hit 0 */
|
|
mutex_unlock(lock);
|
|
return 0;
|
|
}
|
|
/* we hit 0, and we hold the lock */
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(atomic_dec_and_mutex_lock);
|