blob: 525648da693f8caed6934df917f31d6c1f614ce2 [file] [log] [blame]
// 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>
#undef CREATE_TRACE_POINTS
#include <trace/hooks/dtask.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
trace_android_vh_mutex_init(lock);
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)) {
trace_android_vh_record_mutex_lock_starttime(current, jiffies);
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)
{
bool already_on_list = false;
debug_mutex_add_waiter(lock, waiter, current);
trace_android_vh_alter_mutex_list_add(lock, waiter, list, &already_on_list);
if (!already_on_list)
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;
int cnt = 0;
bool time_out = false;
lockdep_assert_preemption_disabled();
while (__mutex_owner(lock) == owner) {
trace_android_vh_mutex_opt_spin_start(lock, &time_out, &cnt);
if (time_out) {
ret = false;
break;
}
/*
* 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);
trace_android_vh_mutex_can_spin_on_owner(lock, &retval);
/*
* 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);
trace_android_vh_mutex_opt_spin_finish(lock, true);
return true;
fail_unlock:
if (!waiter)
osq_unlock(&lock->osq);
fail:
trace_android_vh_mutex_opt_spin_finish(lock, false);
/*
* 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.
*
* 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)) {
trace_android_vh_record_mutex_lock_starttime(current, 0);
return;
}
#endif
__mutex_unlock_slowpath(lock, _RET_IP_);
trace_android_vh_record_mutex_lock_starttime(current, 0);
}
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);
trace_android_vh_record_mutex_lock_starttime(current, jiffies);
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;
}
trace_android_vh_mutex_wait_start(lock);
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);
trace_android_vh_mutex_wait_finish(lock);
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();
trace_android_vh_record_mutex_lock_starttime(current, jiffies);
return 0;
err:
__set_current_state(TASK_RUNNING);
trace_android_vh_mutex_wait_finish(lock);
__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);
trace_android_vh_mutex_unlock_slowpath(lock);
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) {
trace_android_vh_record_mutex_lock_starttime(current, jiffies);
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 */
/**
* 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);