#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/debug_locks.h>
-#include "mcs_spinlock.h"
+#include <linux/osq_lock.h>
/*
* In the DEBUG case we are using the "NULL fastpath" for mutexes,
* 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 mutex must not be freed with
+ * 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.
}
/*
- * after acquiring lock with fastpath or when we lost out in contested
+ * After acquiring lock with fastpath or when we lost out in contested
* slowpath, set ctx and wake up any waiters so they can recheck.
*
* This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set,
spin_unlock_mutex(&lock->base.wait_lock, flags);
}
-
-#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
/*
- * In order to avoid a stampede of mutex spinners from acquiring the mutex
- * more or less simultaneously, the spinners need to acquire a MCS lock
- * first before spinning on the owner field.
+ * After acquiring lock in the slowpath set ctx and wake up any
+ * waiters so they can recheck.
*
+ * Callers must hold the mutex wait_lock.
*/
-
-/*
- * Mutex spinning code migrated from kernel/sched/core.c
- */
-
-static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
+static __always_inline void
+ww_mutex_set_context_slowpath(struct ww_mutex *lock,
+ struct ww_acquire_ctx *ctx)
{
- if (lock->owner != owner)
- return false;
+ struct mutex_waiter *cur;
+
+ ww_mutex_lock_acquired(lock, ctx);
+ lock->ctx = ctx;
/*
- * Ensure we emit the owner->on_cpu, dereference _after_ checking
- * lock->owner still matches owner, if that fails, owner might
- * point to free()d memory, if it still matches, the rcu_read_lock()
- * ensures the memory stays valid.
+ * Give any possible sleeping processes the chance to wake up,
+ * so they can recheck if they have to back off.
*/
- barrier();
-
- return owner->on_cpu;
+ list_for_each_entry(cur, &lock->base.wait_list, list) {
+ debug_mutex_wake_waiter(&lock->base, cur);
+ wake_up_process(cur->task);
+ }
}
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
/*
* Look out! "owner" is an entirely speculative pointer
* access and not reliable.
*/
static noinline
-int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
{
+ bool ret;
+
rcu_read_lock();
- while (owner_running(lock, owner)) {
- if (need_resched())
+ while (true) {
+ /* Return success when the lock owner changed */
+ if (lock->owner != owner) {
+ ret = true;
break;
+ }
+
+ /*
+ * Ensure we emit the owner->on_cpu, dereference _after_
+ * checking lock->owner still matches owner, if that fails,
+ * owner might point to free()d memory, if it still matches,
+ * the rcu_read_lock() ensures the memory stays valid.
+ */
+ barrier();
+
+ if (!owner->on_cpu || need_resched()) {
+ ret = false;
+ break;
+ }
cpu_relax_lowlatency();
}
rcu_read_unlock();
- /*
- * We break out the loop above on need_resched() and when the
- * owner changed, which is a sign for heavy contention. Return
- * success only when lock->owner is NULL.
- */
- return lock->owner == NULL;
+ return ret;
}
/*
if (!mutex_can_spin_on_owner(lock))
goto done;
+ /*
+ * 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 done;
EXPORT_SYMBOL(ww_mutex_unlock);
static inline int __sched
-__mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
+__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 = ACCESS_ONCE(ww->ctx);
}
if (use_ww_ctx && ww_ctx->acquired > 0) {
- ret = __mutex_lock_check_stamp(lock, ww_ctx);
+ ret = __ww_mutex_lock_check_stamp(lock, ww_ctx);
if (ret)
goto err;
}
schedule_preempt_disabled();
spin_lock_mutex(&lock->wait_lock, flags);
}
+ __set_task_state(task, TASK_RUNNING);
+
mutex_remove_waiter(lock, &waiter, current_thread_info());
/* set it to 0 if there are no waiters left: */
if (likely(list_empty(&lock->wait_list)))
if (use_ww_ctx) {
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
- struct mutex_waiter *cur;
-
- /*
- * This branch gets optimized out for the common case,
- * and is only important for ww_mutex_lock.
- */
- ww_mutex_lock_acquired(ww, ww_ctx);
- ww->ctx = ww_ctx;
-
- /*
- * Give any possible sleeping processes the chance to wake up,
- * so they can recheck if they have to back off.
- */
- list_for_each_entry(cur, &lock->wait_list, list) {
- debug_mutex_wake_waiter(lock, cur);
- wake_up_process(cur->task);
- }
+ ww_mutex_set_context_slowpath(ww, ww_ctx);
}
spin_unlock_mutex(&lock->wait_lock, flags);
projects / cascardo / linux.git / blobdiff