From ea9e0fb8fe1bdfca81bd76052a5cce70bb053430 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Nicolai=20H=C3=A4hnle?= Date: Wed, 21 Dec 2016 19:46:32 +0100 Subject: [PATCH] locking/ww_mutex: Set use_ww_ctx even when locking without a context MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Chris Wilson Cc: Daniel Vetter Cc: Linus Torvalds Cc: Maarten Lankhorst Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- include/linux/ww_mutex.h | 11 ++--------- kernel/locking/mutex.c | 29 +++++++++++++++++------------ 2 files changed, 19 insertions(+), 21 deletions(-) diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h index 7b0066814fa0..5f2e8379baff 100644 --- a/include/linux/ww_mutex.h +++ b/include/linux/ww_mutex.h @@ -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); } /** diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 9ad03b9a5f7f..44a64c0a851a 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -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 @@ skip_wait: /* 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; } -- 2.20.1