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locking/ww_mutex: Set use_ww_ctx even when locking without a context

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We will add a new field to struct mutex_waiter.  This field must be
initialized for all waiters if any waiter uses the ww_use_ctx path.

So there is a trade-off: Keep ww_mutex locking without a context on
the faster non-use_ww_ctx path, at the cost of adding the
initialization to all mutex locks (including non-ww_mutexes), or avoid
the additional cost for non-ww_mutex locks, at the cost of adding
additional checks to the use_ww_ctx path.

We take the latter choice.  It may be worth eliminating the users of
ww_mutex_lock(lock, NULL), but there are a lot of them.

Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-5-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Nicolai Hähnle 2016-12-21 19:46:32 +01:00 committed by Ingo Molnar
parent 3822da3ed0
commit ea9e0fb8fe
2 changed files with 19 additions and 21 deletions
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11
include/linux/ww_mutex.h
View File

@ -222,11 +222,7 @@ extern int __must_check __ww_mutex_lock_interruptible(struct ww_mutex *lock,
*/
static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
if (ctx)
return __ww_mutex_lock(lock, ctx);
mutex_lock(&lock->base);
return 0;
return __ww_mutex_lock(lock, ctx);
}
/**
@ -262,10 +258,7 @@ static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ct
static inline int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock,
struct ww_acquire_ctx *ctx)
{
if (ctx)
return __ww_mutex_lock_interruptible(lock, ctx);
else
return mutex_lock_interruptible(&lock->base);
return __ww_mutex_lock_interruptible(lock, ctx);
}
/**

29
kernel/locking/mutex.c
View File

@ -469,7 +469,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
for (;;) {
struct task_struct *owner;
if (use_ww_ctx && ww_ctx->acquired > 0) {
if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) {
struct ww_mutex *ww;
ww = container_of(lock, struct ww_mutex, base);
@ -629,8 +629,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
struct ww_mutex *ww;
int ret;
if (use_ww_ctx) {
ww = container_of(lock, struct ww_mutex, base);
ww = container_of(lock, struct ww_mutex, base);
if (use_ww_ctx && ww_ctx) {
if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
return -EALREADY;
}
@ -642,7 +643,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, false)) {
/* got the lock, yay! */
lock_acquired(&lock->dep_map, ip);
if (use_ww_ctx)
if (use_ww_ctx && ww_ctx)
ww_mutex_set_context_fastpath(ww, ww_ctx);
preempt_enable();
return 0;
@ -688,7 +689,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
goto err;
}
if (use_ww_ctx && ww_ctx->acquired > 0) {
if (use_ww_ctx && ww_ctx && ww_ctx->acquired > 0) {
ret = __ww_mutex_lock_check_stamp(lock, ww_ctx);
if (ret)
goto err;
@ -728,7 +729,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
/* got the lock - cleanup and rejoice! */
lock_acquired(&lock->dep_map, ip);
if (use_ww_ctx)
if (use_ww_ctx && ww_ctx)
ww_mutex_set_context_slowpath(ww, ww_ctx);
spin_unlock_mutex(&lock->wait_lock, flags);
@ -816,8 +817,9 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
might_sleep();
ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
0, &ctx->dep_map, _RET_IP_, ctx, 1);
if (!ret && ctx->acquired > 1)
0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
ctx, 1);
if (!ret && ctx && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
return ret;
@ -831,9 +833,10 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
might_sleep();
ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
0, &ctx->dep_map, _RET_IP_, ctx, 1);
0, ctx ? &ctx->dep_map : NULL, _RET_IP_,
ctx, 1);
if (!ret && ctx->acquired > 1)
if (!ret && ctx && ctx->acquired > 1)
return ww_mutex_deadlock_injection(lock, ctx);
return ret;
@ -1021,7 +1024,8 @@ __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);
if (ctx)
ww_mutex_set_context_fastpath(lock, ctx);
return 0;
}
@ -1035,7 +1039,8 @@ __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);
if (ctx)
ww_mutex_set_context_fastpath(lock, ctx);
return 0;
}