Author | Tokens | Token Proportion | Commits | Commit Proportion |
---|---|---|---|---|
Peter Zijlstra | 1300 | 37.35% | 29 | 25.44% |
Ingo Molnar | 648 | 18.62% | 11 | 9.65% |
Maarten Lankhorst | 451 | 12.96% | 5 | 4.39% |
Nicolai Hähnle | 161 | 4.63% | 8 | 7.02% |
Thomas Hellstrom | 158 | 4.54% | 1 | 0.88% |
Daniel Vetter | 127 | 3.65% | 1 | 0.88% |
Davidlohr Bueso A | 118 | 3.39% | 9 | 7.89% |
Liam R. Howlett | 74 | 2.13% | 1 | 0.88% |
Waiman Long | 71 | 2.04% | 6 | 5.26% |
Tejun Heo | 62 | 1.78% | 1 | 0.88% |
Eric Paris | 57 | 1.64% | 1 | 0.88% |
Neil Brown | 43 | 1.24% | 1 | 0.88% |
Jason Low | 33 | 0.95% | 5 | 4.39% |
Zhang Qiang | 28 | 0.80% | 1 | 0.88% |
Sebastian Andrzej Siewior | 21 | 0.60% | 2 | 1.75% |
Namhyung Kim | 20 | 0.57% | 1 | 0.88% |
Thomas Gleixner | 19 | 0.55% | 4 | 3.51% |
Chris Wilson | 17 | 0.49% | 1 | 0.88% |
Brian Foster | 10 | 0.29% | 1 | 0.88% |
Mukesh Ojha | 9 | 0.26% | 2 | 1.75% |
Andrew Morton | 6 | 0.17% | 2 | 1.75% |
John Levon | 6 | 0.17% | 1 | 0.88% |
Yanfei Xu | 6 | 0.17% | 1 | 0.88% |
Tetsuo Handa | 4 | 0.11% | 1 | 0.88% |
Kefeng Wang | 4 | 0.11% | 1 | 0.88% |
Clark Williams | 3 | 0.09% | 1 | 0.88% |
Harvey Harrison | 3 | 0.09% | 1 | 0.88% |
Matthew Wilcox | 3 | 0.09% | 1 | 0.88% |
Steven Rostedt | 3 | 0.09% | 1 | 0.88% |
Christian Bornträger | 2 | 0.06% | 1 | 0.88% |
Tim Chen | 2 | 0.06% | 1 | 0.88% |
Oleg Nesterov | 2 | 0.06% | 1 | 0.88% |
Mauro Carvalho Chehab | 2 | 0.06% | 2 | 1.75% |
Pan Xinhui | 1 | 0.03% | 1 | 0.88% |
Paul Gortmaker | 1 | 0.03% | 1 | 0.88% |
Jann Horn | 1 | 0.03% | 1 | 0.88% |
Frédéric Weisbecker | 1 | 0.03% | 1 | 0.88% |
Yaowei Bai | 1 | 0.03% | 1 | 0.88% |
Randy Dunlap | 1 | 0.03% | 1 | 0.88% |
Török Edwin | 1 | 0.03% | 1 | 0.88% |
Roman Zippel | 1 | 0.03% | 1 | 0.88% |
Total | 3481 | 114 |
// SPDX-License-Identifier: GPL-2.0-only /* * kernel/locking/mutex.c * * Mutexes: blocking mutual exclusion locks * * Started by Ingo Molnar: * * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and * David Howells for suggestions and improvements. * * - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline * from the -rt tree, where it was originally implemented for rtmutexes * by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale * and Sven Dietrich. * * Also see Documentation/locking/mutex-design.rst. */ #include <linux/mutex.h> #include <linux/ww_mutex.h> #include <linux/sched/signal.h> #include <linux/sched/rt.h> #include <linux/sched/wake_q.h> #include <linux/sched/debug.h> #include <linux/export.h> #include <linux/spinlock.h> #include <linux/interrupt.h> #include <linux/debug_locks.h> #include <linux/osq_lock.h> #define CREATE_TRACE_POINTS #include <trace/events/lock.h> #ifndef CONFIG_PREEMPT_RT #include "mutex.h" #ifdef CONFIG_DEBUG_MUTEXES # define MUTEX_WARN_ON(cond) DEBUG_LOCKS_WARN_ON(cond) #else # define MUTEX_WARN_ON(cond) #endif void __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) { atomic_long_set(&lock->owner, 0); raw_spin_lock_init(&lock->wait_lock); INIT_LIST_HEAD(&lock->wait_list); #ifdef CONFIG_MUTEX_SPIN_ON_OWNER osq_lock_init(&lock->osq); #endif debug_mutex_init(lock, name, key); } EXPORT_SYMBOL(__mutex_init); /* * @owner: contains: 'struct task_struct *' to the current lock owner, * NULL means not owned. Since task_struct pointers are aligned at * at least L1_CACHE_BYTES, we have low bits to store extra state. * * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup. * Bit1 indicates unlock needs to hand the lock to the top-waiter * Bit2 indicates handoff has been done and we're waiting for pickup. */ #define MUTEX_FLAG_WAITERS 0x01 #define MUTEX_FLAG_HANDOFF 0x02 #define MUTEX_FLAG_PICKUP 0x04 #define MUTEX_FLAGS 0x07 /* * Internal helper function; C doesn't allow us to hide it :/ * * DO NOT USE (outside of mutex code). */ static inline struct task_struct *__mutex_owner(struct mutex *lock) { return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS); } static inline struct task_struct *__owner_task(unsigned long owner) { return (struct task_struct *)(owner & ~MUTEX_FLAGS); } bool mutex_is_locked(struct mutex *lock) { return __mutex_owner(lock) != NULL; } EXPORT_SYMBOL(mutex_is_locked); static inline unsigned long __owner_flags(unsigned long owner) { return owner & MUTEX_FLAGS; } /* * Returns: __mutex_owner(lock) on failure or NULL on success. */ static inline struct task_struct *__mutex_trylock_common(struct mutex *lock, bool handoff) { unsigned long owner, curr = (unsigned long)current; owner = atomic_long_read(&lock->owner); for (;;) { /* must loop, can race against a flag */ unsigned long flags = __owner_flags(owner); unsigned long task = owner & ~MUTEX_FLAGS; if (task) { if (flags & MUTEX_FLAG_PICKUP) { if (task != curr) break; flags &= ~MUTEX_FLAG_PICKUP; } else if (handoff) { if (flags & MUTEX_FLAG_HANDOFF) break; flags |= MUTEX_FLAG_HANDOFF; } else { break; } } else { MUTEX_WARN_ON(flags & (MUTEX_FLAG_HANDOFF | MUTEX_FLAG_PICKUP)); task = curr; } if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, task | flags)) { if (task == curr) return NULL; break; } } return __owner_task(owner); } /* * Trylock or set HANDOFF */ static inline bool __mutex_trylock_or_handoff(struct mutex *lock, bool handoff) { return !__mutex_trylock_common(lock, handoff); } /* * Actual trylock that will work on any unlocked state. */ static inline bool __mutex_trylock(struct mutex *lock) { return !__mutex_trylock_common(lock, false); } #ifndef CONFIG_DEBUG_LOCK_ALLOC /* * Lockdep annotations are contained to the slow paths for simplicity. * There is nothing that would stop spreading the lockdep annotations outwards * except more code. */ /* * Optimistic trylock that only works in the uncontended case. Make sure to * follow with a __mutex_trylock() before failing. */ static __always_inline bool __mutex_trylock_fast(struct mutex *lock) { unsigned long curr = (unsigned long)current; unsigned long zero = 0UL; if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr)) return true; return false; } static __always_inline bool __mutex_unlock_fast(struct mutex *lock) { unsigned long curr = (unsigned long)current; return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL); } #endif static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag) { atomic_long_or(flag, &lock->owner); } static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag) { atomic_long_andnot(flag, &lock->owner); } static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter) { return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter; } /* * Add @waiter to a given location in the lock wait_list and set the * FLAG_WAITERS flag if it's the first waiter. */ static void __mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, struct list_head *list) { debug_mutex_add_waiter(lock, waiter, current); list_add_tail(&waiter->list, list); if (__mutex_waiter_is_first(lock, waiter)) __mutex_set_flag(lock, MUTEX_FLAG_WAITERS); } static void __mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter) { list_del(&waiter->list); if (likely(list_empty(&lock->wait_list))) __mutex_clear_flag(lock, MUTEX_FLAGS); debug_mutex_remove_waiter(lock, waiter, current); } /* * Give up ownership to a specific task, when @task = NULL, this is equivalent * to a regular unlock. Sets PICKUP on a handoff, clears HANDOFF, preserves * WAITERS. Provides RELEASE semantics like a regular unlock, the * __mutex_trylock() provides a matching ACQUIRE semantics for the handoff. */ static void __mutex_handoff(struct mutex *lock, struct task_struct *task) { unsigned long owner = atomic_long_read(&lock->owner); for (;;) { unsigned long new; MUTEX_WARN_ON(__owner_task(owner) != current); MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP); new = (owner & MUTEX_FLAG_WAITERS); new |= (unsigned long)task; if (task) new |= MUTEX_FLAG_PICKUP; if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, new)) break; } } #ifndef CONFIG_DEBUG_LOCK_ALLOC /* * We split the mutex lock/unlock logic into separate fastpath and * slowpath functions, to reduce the register pressure on the fastpath. * We also put the fastpath first in the kernel image, to make sure the * branch is predicted by the CPU as default-untaken. */ static void __sched __mutex_lock_slowpath(struct mutex *lock); /** * mutex_lock - acquire the mutex * @lock: the mutex to be acquired * * Lock the mutex exclusively for this task. If the mutex is not * available right now, it will sleep until it can get it. * * The mutex must later on be released by the same task that * acquired it. Recursive locking is not allowed. The task * may not exit without first unlocking the mutex. Also, kernel * memory where the mutex resides must not be freed with * the mutex still locked. The mutex must first be initialized * (or statically defined) before it can be locked. memset()-ing * the mutex to 0 is not allowed. * * (The CONFIG_DEBUG_MUTEXES .config option turns on debugging * checks that will enforce the restrictions and will also do * deadlock debugging) * * This function is similar to (but not equivalent to) down(). */ void __sched mutex_lock(struct mutex *lock) { might_sleep(); if (!__mutex_trylock_fast(lock)) __mutex_lock_slowpath(lock); } EXPORT_SYMBOL(mutex_lock); #endif #include "ww_mutex.h" #ifdef CONFIG_MUTEX_SPIN_ON_OWNER /* * Trylock variant that returns the owning task on failure. */ static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock) { return __mutex_trylock_common(lock, false); } static inline bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter) { struct ww_mutex *ww; ww = container_of(lock, struct ww_mutex, base); /* * If ww->ctx is set the contents are undefined, only * 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. * * Check this in every inner iteration because we may * be racing against another thread's ww_mutex_lock. */ if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx)) return false; /* * If we aren't on the wait list yet, cancel the spin * if there are waiters. We want to avoid stealing the * lock from a waiter with an earlier stamp, since the * other thread may already own a lock that we also * need. */ if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS)) return false; /* * Similarly, stop spinning if we are no longer the * first waiter. */ if (waiter && !__mutex_waiter_is_first(lock, waiter)) return false; return true; } /* * Look out! "owner" is an entirely speculative pointer access and not * reliable. * * "noinline" so that this function shows up on perf profiles. */ static noinline bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner, struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter) { bool ret = true; lockdep_assert_preemption_disabled(); while (__mutex_owner(lock) == owner) { /* * Ensure we emit the owner->on_cpu, dereference _after_ * checking lock->owner still matches owner. And we already * disabled preemption which is equal to the RCU read-side * crital section in optimistic spinning code. Thus the * task_strcut structure won't go away during the spinning * period */ barrier(); /* * Use vcpu_is_preempted to detect lock holder preemption issue. */ if (!owner_on_cpu(owner) || need_resched()) { ret = false; break; } if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) { ret = false; break; } cpu_relax(); } return ret; } /* * Initial check for entering the mutex spinning loop */ static inline int mutex_can_spin_on_owner(struct mutex *lock) { struct task_struct *owner; int retval = 1; lockdep_assert_preemption_disabled(); if (need_resched()) return 0; /* * We already disabled preemption which is equal to the RCU read-side * crital section in optimistic spinning code. Thus the task_strcut * structure won't go away during the spinning period. */ owner = __mutex_owner(lock); if (owner) retval = owner_on_cpu(owner); /* * If lock->owner is not set, the mutex has been released. Return true * such that we'll trylock in the spin path, which is a faster option * than the blocking slow path. */ return retval; } /* * Optimistic spinning. * * We try to spin for acquisition when we find that the lock owner * is currently running on a (different) CPU and while we don't * need to reschedule. The rationale is that if the lock owner is * running, it is likely to release the lock soon. * * The mutex spinners are queued up using MCS lock so that only one * spinner can compete for the mutex. However, if mutex spinning isn't * going to happen, there is no point in going through the lock/unlock * overhead. * * Returns true when the lock was taken, otherwise false, indicating * that we need to jump to the slowpath and sleep. * * The waiter flag is set to true if the spinner is a waiter in the wait * queue. The waiter-spinner will spin on the lock directly and concurrently * with the spinner at the head of the OSQ, if present, until the owner is * changed to itself. */ static __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter) { if (!waiter) { /* * The purpose of the mutex_can_spin_on_owner() function is * to eliminate the overhead of osq_lock() and osq_unlock() * in case spinning isn't possible. As a waiter-spinner * is not going to take OSQ lock anyway, there is no need * to call mutex_can_spin_on_owner(). */ if (!mutex_can_spin_on_owner(lock)) goto fail; /* * In order to avoid a stampede of mutex spinners trying to * acquire the mutex all at once, the spinners need to take a * MCS (queued) lock first before spinning on the owner field. */ if (!osq_lock(&lock->osq)) goto fail; } for (;;) { struct task_struct *owner; /* Try to acquire the mutex... */ owner = __mutex_trylock_or_owner(lock); if (!owner) break; /* * There's an owner, wait for it to either * release the lock or go to sleep. */ if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter)) goto fail_unlock; /* * 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 * values at the cost of a few extra spins. */ cpu_relax(); } 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 __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *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. * * The caller must ensure that the mutex stays alive until this function has * returned - mutex_unlock() can NOT directly be used to release an object such * that another concurrent task can free it. * Mutexes are different from spinlocks & refcounts in this aspect. * * 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) { __ww_mutex_unlock(lock); mutex_unlock(&lock->base); } EXPORT_SYMBOL(ww_mutex_unlock); /* * Lock a mutex (possibly interruptible), slowpath: */ static __always_inline int __sched __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclass, struct lockdep_map *nest_lock, unsigned long ip, struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx) { struct mutex_waiter waiter; struct ww_mutex *ww; int ret; if (!use_ww_ctx) ww_ctx = NULL; might_sleep(); MUTEX_WARN_ON(lock->magic != lock); ww = container_of(lock, struct ww_mutex, base); if (ww_ctx) { if (unlikely(ww_ctx == READ_ONCE(ww->ctx))) return -EALREADY; /* * Reset the wounded flag after a kill. No other process can * race and wound us here since they can't have a valid owner * pointer if we don't have any locks held. */ if (ww_ctx->acquired == 0) ww_ctx->wounded = 0; #ifdef CONFIG_DEBUG_LOCK_ALLOC nest_lock = &ww_ctx->dep_map; #endif } preempt_disable(); mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip); trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN); if (__mutex_trylock(lock) || mutex_optimistic_spin(lock, ww_ctx, NULL)) { /* got the lock, yay! */ lock_acquired(&lock->dep_map, ip); if (ww_ctx) ww_mutex_set_context_fastpath(ww, ww_ctx); trace_contention_end(lock, 0); preempt_enable(); return 0; } raw_spin_lock(&lock->wait_lock); /* * After waiting to acquire the wait_lock, try again. */ if (__mutex_trylock(lock)) { if (ww_ctx) __ww_mutex_check_waiters(lock, ww_ctx); goto skip_wait; } debug_mutex_lock_common(lock, &waiter); waiter.task = current; if (use_ww_ctx) waiter.ww_ctx = ww_ctx; lock_contended(&lock->dep_map, ip); if (!use_ww_ctx) { /* add waiting tasks to the end of the waitqueue (FIFO): */ __mutex_add_waiter(lock, &waiter, &lock->wait_list); } else { /* * Add in stamp order, waking up waiters that must kill * themselves. */ ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx); if (ret) goto err_early_kill; } set_current_state(state); trace_contention_begin(lock, LCB_F_MUTEX); for (;;) { bool first; /* * 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)) goto acquired; /* * Check for signals and kill conditions while holding * wait_lock. This ensures the lock cancellation is ordered * against mutex_unlock() and wake-ups do not go missing. */ if (signal_pending_state(state, current)) { ret = -EINTR; goto err; } if (ww_ctx) { ret = __ww_mutex_check_kill(lock, &waiter, ww_ctx); if (ret) goto err; } raw_spin_unlock(&lock->wait_lock); schedule_preempt_disabled(); first = __mutex_waiter_is_first(lock, &waiter); set_current_state(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 (__mutex_trylock_or_handoff(lock, first)) break; if (first) { trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN); if (mutex_optimistic_spin(lock, ww_ctx, &waiter)) break; trace_contention_begin(lock, LCB_F_MUTEX); } raw_spin_lock(&lock->wait_lock); } raw_spin_lock(&lock->wait_lock); acquired: __set_current_state(TASK_RUNNING); if (ww_ctx) { /* * Wound-Wait; we stole the lock (!first_waiter), check the * waiters as anyone might want to wound us. */ if (!ww_ctx->is_wait_die && !__mutex_waiter_is_first(lock, &waiter)) __ww_mutex_check_waiters(lock, ww_ctx); } __mutex_remove_waiter(lock, &waiter); debug_mutex_free_waiter(&waiter); skip_wait: /* got the lock - cleanup and rejoice! */ lock_acquired(&lock->dep_map, ip); trace_contention_end(lock, 0); if (ww_ctx) ww_mutex_lock_acquired(ww, ww_ctx); raw_spin_unlock(&lock->wait_lock); preempt_enable(); return 0; err: __set_current_state(TASK_RUNNING); __mutex_remove_waiter(lock, &waiter); err_early_kill: trace_contention_end(lock, ret); raw_spin_unlock(&lock->wait_lock); debug_mutex_free_waiter(&waiter); mutex_release(&lock->dep_map, ip); preempt_enable(); return ret; } static int __sched __mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass, struct lockdep_map *nest_lock, unsigned long ip) { return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false); } static int __sched __ww_mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass, unsigned long ip, struct ww_acquire_ctx *ww_ctx) { return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx, true); } /** * ww_mutex_trylock - tries to acquire the w/w mutex with optional acquire context * @ww: mutex to lock * @ww_ctx: optional w/w acquire context * * Trylocks a mutex with the optional acquire context; no deadlock detection is * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise. * * Unlike ww_mutex_lock, no deadlock handling is performed. However, if a @ctx is * specified, -EALREADY handling may happen in calls to ww_mutex_trylock. * * A mutex acquired with this function must be released with ww_mutex_unlock. */ int ww_mutex_trylock(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx) { if (!ww_ctx) return mutex_trylock(&ww->base); MUTEX_WARN_ON(ww->base.magic != &ww->base); /* * Reset the wounded flag after a kill. No other process can * race and wound us here, since they can't have a valid owner * pointer if we don't have any locks held. */ if (ww_ctx->acquired == 0) ww_ctx->wounded = 0; if (__mutex_trylock(&ww->base)) { ww_mutex_set_context_fastpath(ww, ww_ctx); mutex_acquire_nest(&ww->base.dep_map, 0, 1, &ww_ctx->dep_map, _RET_IP_); return 1; } return 0; } EXPORT_SYMBOL(ww_mutex_trylock); #ifdef CONFIG_DEBUG_LOCK_ALLOC void __sched mutex_lock_nested(struct mutex *lock, unsigned int subclass) { __mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_); } EXPORT_SYMBOL_GPL(mutex_lock_nested); void __sched _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest) { __mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_); } EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock); int __sched mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass) { return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_); } EXPORT_SYMBOL_GPL(mutex_lock_killable_nested); int __sched mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass) { return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_); } 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 = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, _RET_IP_, ctx); if (!ret && ctx && 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 = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, _RET_IP_, ctx); if (!ret && ctx && 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; DEFINE_WAKE_Q(wake_q); unsigned long owner; mutex_release(&lock->dep_map, 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 (;;) { MUTEX_WARN_ON(__owner_task(owner) != current); MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP); if (owner & MUTEX_FLAG_HANDOFF) break; if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(owner))) { if (owner & MUTEX_FLAG_WAITERS) break; return; } } raw_spin_lock(&lock->wait_lock); 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); raw_spin_unlock(&lock->wait_lock); 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 by signals. * @lock: The mutex to be acquired. * * Lock the mutex like mutex_lock(). If a signal is delivered while the * process is sleeping, this function will return without acquiring the * mutex. * * Context: Process context. * Return: 0 if the lock was successfully acquired or %-EINTR if a * signal arrived. */ 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); /** * mutex_lock_killable() - Acquire the mutex, interruptible by fatal signals. * @lock: The mutex to be acquired. * * Lock the mutex like mutex_lock(). If a signal which will be fatal to * the current process is delivered while the process is sleeping, this * function will return without acquiring the mutex. * * Context: Process context. * Return: 0 if the lock was successfully acquired or %-EINTR if a * fatal signal arrived. */ 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); /** * mutex_lock_io() - Acquire the mutex and mark the process as waiting for I/O * @lock: The mutex to be acquired. * * Lock the mutex like mutex_lock(). While the task is waiting for this * mutex, it will be accounted as being in the IO wait state by the * scheduler. * * Context: Process context. */ 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(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_); } static noinline int __sched __mutex_lock_killable_slowpath(struct mutex *lock) { return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_); } static noinline int __sched __mutex_lock_interruptible_slowpath(struct mutex *lock) { return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_); } static noinline int __sched __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) { return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0, _RET_IP_, ctx); } static noinline int __sched __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) { return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0, _RET_IP_, ctx); } #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_WARN_ON(lock->magic != lock); locked = __mutex_trylock(lock); 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)) { if (ctx) 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)) { if (ctx) ww_mutex_set_context_fastpath(lock, ctx); return 0; } return __ww_mutex_lock_interruptible_slowpath(lock, ctx); } EXPORT_SYMBOL(ww_mutex_lock_interruptible); #endif /* !CONFIG_DEBUG_LOCK_ALLOC */ #endif /* !CONFIG_PREEMPT_RT */ EXPORT_TRACEPOINT_SYMBOL_GPL(contention_begin); EXPORT_TRACEPOINT_SYMBOL_GPL(contention_end); /** * 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);
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