[PATCH v2 01/12] locking/ww_mutex: Remove wakeups from under mutex::wait_lock

John Stultz
2023-03-20T23:37:42Z

From: Peter Zijlstra <peterz@infradead.org>

In preparation to nest mutex::wait_lock under rq::lock we need to remove
wakeups from under it.

Cc: Joel Fernandes <joelaf@google.com>
Cc: Qais Yousef <qyousef@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Zimuzo Ezeozue <zezeozue@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: kernel-team@android.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
v2:
* Move wake_q_init() as suggested by Waiman Long
---
include/linux/ww_mutex.h | 3 +++
kernel/locking/mutex.c | 8 ++++++++
kernel/locking/ww_mutex.h | 10 ++++++++--
3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index bb763085479a..9335b2202017 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -19,6 +19,7 @@

#include <linux/mutex.h>
#include <linux/rtmutex.h>
+#include <linux/sched/wake_q.h>

#if defined(CONFIG_DEBUG_MUTEXES) || \
(defined(CONFIG_PREEMPT_RT) && defined(CONFIG_DEBUG_RT_MUTEXES))
@@ -58,6 +59,7 @@ struct ww_acquire_ctx {
unsigned int acquired;
unsigned short wounded;
unsigned short is_wait_die;
+ struct wake_q_head wake_q;
#ifdef DEBUG_WW_MUTEXES
unsigned int done_acquire;
struct ww_class *ww_class;
@@ -137,6 +139,7 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
ctx->acquired = 0;
ctx->wounded = false;
ctx->is_wait_die = ww_class->is_wait_die;
+ wake_q_init(&ctx->wake_q);
#ifdef DEBUG_WW_MUTEXES
ctx->ww_class = ww_class;
ctx->done_acquire = 0;
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index d973fe6041bf..1582756914df 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -676,6 +676,8 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
}

raw_spin_unlock(&lock->wait_lock);
+ if (ww_ctx)
+ ww_ctx_wake(ww_ctx);
schedule_preempt_disabled();

first = __mutex_waiter_is_first(lock, &waiter);
@@ -725,6 +727,8 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
ww_mutex_lock_acquired(ww, ww_ctx);

raw_spin_unlock(&lock->wait_lock);
+ if (ww_ctx)
+ ww_ctx_wake(ww_ctx);
preempt_enable();
return 0;

@@ -736,6 +740,8 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
raw_spin_unlock(&lock->wait_lock);
debug_mutex_free_waiter(&waiter);
mutex_release(&lock->dep_map, ip);
+ if (ww_ctx)
+ ww_ctx_wake(ww_ctx);
preempt_enable();
return ret;
}
@@ -946,9 +952,11 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
if (owner & MUTEX_FLAG_HANDOFF)
__mutex_handoff(lock, next);

+ preempt_disable();
raw_spin_unlock(&lock->wait_lock);

wake_up_q(&wake_q);
+ preempt_enable();
}

#ifndef CONFIG_DEBUG_LOCK_ALLOC
diff --git a/kernel/locking/ww_mutex.h b/kernel/locking/ww_mutex.h
index 56f139201f24..e49ea5336473 100644
--- a/kernel/locking/ww_mutex.h
+++ b/kernel/locking/ww_mutex.h
@@ -161,6 +161,12 @@ static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock)

#endif /* WW_RT */

+void ww_ctx_wake(struct ww_acquire_ctx *ww_ctx)
+{
+ wake_up_q(&ww_ctx->wake_q);
+ wake_q_init(&ww_ctx->wake_q);
+}
+
/*
* Wait-Die:
* The newer transactions are killed when:
@@ -284,7 +290,7 @@ __ww_mutex_die(struct MUTEX *lock, struct MUTEX_WAITER *waiter,
#ifndef WW_RT
debug_mutex_wake_waiter(lock, waiter);
#endif
- wake_up_process(waiter->task);
+ wake_q_add(&ww_ctx->wake_q, waiter->task);
}

return true;
@@ -331,7 +337,7 @@ static bool __ww_mutex_wound(struct MUTEX *lock,
* wakeup pending to re-read the wounded state.
*/
if (owner != current)
- wake_up_process(owner);
+ wake_q_add(&ww_ctx->wake_q, owner);

return true;
}
--
2.40.0.rc1.284.g88254d51c5-goog