From: Waiman Long longman@redhat.com
[ Upstream commit 5de2055d31ea88fd9ae9709ac95c372a505a60fa ]
The use_ww_ctx flag is passed to mutex_optimistic_spin(), but the function doesn't use it. The frequent use of the (use_ww_ctx && ww_ctx) combination is repetitive.
In fact, ww_ctx should not be used at all if !use_ww_ctx. Simplify ww_mutex code by dropping use_ww_ctx from mutex_optimistic_spin() an clear ww_ctx if !use_ww_ctx. In this way, we can replace (use_ww_ctx && ww_ctx) by just (ww_ctx).
Signed-off-by: Waiman Long longman@redhat.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Davidlohr Bueso dbueso@suse.de Link: https://lore.kernel.org/r/20210316153119.13802-2-longman@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/locking/mutex.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 468a9b8422e3..07a9f9f46e03 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -636,7 +636,7 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock) */ static __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, - const bool use_ww_ctx, struct mutex_waiter *waiter) + struct mutex_waiter *waiter) { if (!waiter) { /* @@ -712,7 +712,7 @@ mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, #else static __always_inline bool mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx, - const bool use_ww_ctx, struct mutex_waiter *waiter) + struct mutex_waiter *waiter) { return false; } @@ -932,6 +932,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, struct ww_mutex *ww; int ret;
+ if (!use_ww_ctx) + ww_ctx = NULL; + might_sleep();
#ifdef CONFIG_DEBUG_MUTEXES @@ -939,7 +942,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, #endif
ww = container_of(lock, struct ww_mutex, base); - if (use_ww_ctx && ww_ctx) { + if (ww_ctx) { if (unlikely(ww_ctx == READ_ONCE(ww->ctx))) return -EALREADY;
@@ -956,10 +959,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
if (__mutex_trylock(lock) || - mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, NULL)) { + mutex_optimistic_spin(lock, ww_ctx, NULL)) { /* got the lock, yay! */ lock_acquired(&lock->dep_map, ip); - if (use_ww_ctx && ww_ctx) + if (ww_ctx) ww_mutex_set_context_fastpath(ww, ww_ctx); preempt_enable(); return 0; @@ -970,7 +973,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * After waiting to acquire the wait_lock, try again. */ if (__mutex_trylock(lock)) { - if (use_ww_ctx && ww_ctx) + if (ww_ctx) __ww_mutex_check_waiters(lock, ww_ctx);
goto skip_wait; @@ -1023,7 +1026,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, goto err; }
- if (use_ww_ctx && ww_ctx) { + if (ww_ctx) { ret = __ww_mutex_check_kill(lock, &waiter, ww_ctx); if (ret) goto err; @@ -1036,7 +1039,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * ww_mutex needs to always recheck its position since its waiter * list is not FIFO ordered. */ - if ((use_ww_ctx && ww_ctx) || !first) { + if (ww_ctx || !first) { first = __mutex_waiter_is_first(lock, &waiter); if (first) __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF); @@ -1049,7 +1052,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * or we must see its unlock and acquire. */ if (__mutex_trylock(lock) || - (first && mutex_optimistic_spin(lock, ww_ctx, use_ww_ctx, &waiter))) + (first && mutex_optimistic_spin(lock, ww_ctx, &waiter))) break;
spin_lock(&lock->wait_lock); @@ -1058,7 +1061,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, acquired: __set_current_state(TASK_RUNNING);
- if (use_ww_ctx && ww_ctx) { + if (ww_ctx) { /* * Wound-Wait; we stole the lock (!first_waiter), check the * waiters as anyone might want to wound us. @@ -1078,7 +1081,7 @@ __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 && ww_ctx) + if (ww_ctx) ww_mutex_lock_acquired(ww, ww_ctx);
spin_unlock(&lock->wait_lock);