From dc1f7893a70fe403983bd8492f177bf993940e2c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 30 Mar 2022 13:06:54 +0200 Subject: [PATCH] locking/mutex: Make contention tracepoints more consistent wrt adaptive spinning Have the trace_contention_*() tracepoints consistently include adaptive spinning. In order to differentiate between the spinning and non-spinning states add LCB_F_MUTEX and combine with LCB_F_SPIN. The consequence is that a mutex contention can now triggler multiple _begin() tracepoints before triggering an _end(). Additionally, this fixes one path where mutex would trigger _end() without ever seeing a _begin(). Signed-off-by: Peter Zijlstra (Intel) --- include/trace/events/lock.h | 4 +++- kernel/locking/mutex.c | 16 ++++++++++++---- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h index b9b6e3edd518..9ebd081e057e 100644 --- a/include/trace/events/lock.h +++ b/include/trace/events/lock.h @@ -14,6 +14,7 @@ #define LCB_F_WRITE (1U << 2) #define LCB_F_RT (1U << 3) #define LCB_F_PERCPU (1U << 4) +#define LCB_F_MUTEX (1U << 5) #ifdef CONFIG_LOCKDEP @@ -113,7 +114,8 @@ TRACE_EVENT(contention_begin, { LCB_F_READ, "READ" }, { LCB_F_WRITE, "WRITE" }, { LCB_F_RT, "RT" }, - { LCB_F_PERCPU, "PERCPU" } + { LCB_F_PERCPU, "PERCPU" }, + { LCB_F_MUTEX, "MUTEX" } )) ); diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index c88deda77cf2..d973fe6041bf 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -602,12 +602,14 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas 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); preempt_enable(); return 0; } @@ -644,7 +646,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas } set_current_state(state); - trace_contention_begin(lock, 0); + trace_contention_begin(lock, LCB_F_MUTEX); for (;;) { bool first; @@ -684,10 +686,16 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas * 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) || - (first && mutex_optimistic_spin(lock, ww_ctx, &waiter))) + 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); @@ -723,8 +731,8 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas err: __set_current_state(TASK_RUNNING); __mutex_remove_waiter(lock, &waiter); - trace_contention_end(lock, ret); 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);