locking/mutex: Make mutex::wait_lock irq safe

With the proxy-execution series, we traverse the task->mutex->task
blocked_on/owner chain in the scheduler core. We do this while holding
the rq::lock to keep the structures in place while taking and
releasing the alternating lock types.

Since the mutex::wait_lock is one of the locks we will take in this
way under the rq::lock in the scheduler core, we need to make sure
that its usage elsewhere is irq safe.

[rebase & fix {un,}lock_wait_lock helpers in ww_mutex.h]
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Metin Kaya <metin.kaya@arm.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: Metin Kaya <metin.kaya@arm.com>
Link: https://lore.kernel.org/r/20241009235352.1614323-3-jstultz@google.com

kernel/locking/mutex.c

@@ -578,6 +578,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 	DEFINE_WAKE_Q(wake_q);
 	struct mutex_waiter waiter;
 	struct ww_mutex *ww;
+	unsigned long flags;
 	int ret;
 
 	if (!use_ww_ctx)
@@ -620,7 +621,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 		return 0;
 	}
 
-	raw_spin_lock(&lock->wait_lock);
+	raw_spin_lock_irqsave(&lock->wait_lock, flags);
 	/*
 	 * After waiting to acquire the wait_lock, try again.
 	 */
@@ -681,7 +682,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 				goto err;
 		}
 
-		raw_spin_unlock(&lock->wait_lock);
+		raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
 		/* Make sure we do wakeups before calling schedule */
 		wake_up_q(&wake_q);
 		wake_q_init(&wake_q);
@@ -706,9 +707,9 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 			trace_contention_begin(lock, LCB_F_MUTEX);
 		}
 
-		raw_spin_lock(&lock->wait_lock);
+		raw_spin_lock_irqsave(&lock->wait_lock, flags);
 	}
-	raw_spin_lock(&lock->wait_lock);
+	raw_spin_lock_irqsave(&lock->wait_lock, flags);
 acquired:
 	__set_current_state(TASK_RUNNING);
 
@@ -734,7 +735,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 	if (ww_ctx)
 		ww_mutex_lock_acquired(ww, ww_ctx);
 
-	raw_spin_unlock(&lock->wait_lock);
+	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
 	wake_up_q(&wake_q);
 	preempt_enable();
 	return 0;
@@ -744,7 +745,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
 	__mutex_remove_waiter(lock, &waiter);
 err_early_kill:
 	trace_contention_end(lock, ret);
-	raw_spin_unlock(&lock->wait_lock);
+	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
 	debug_mutex_free_waiter(&waiter);
 	mutex_release(&lock->dep_map, ip);
 	wake_up_q(&wake_q);
@@ -915,6 +916,7 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
 	struct task_struct *next = NULL;
 	DEFINE_WAKE_Q(wake_q);
 	unsigned long owner;
+	unsigned long flags;
 
 	mutex_release(&lock->dep_map, ip);
 
@@ -941,7 +943,7 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
 		}
 	}
 
-	raw_spin_lock(&lock->wait_lock);
+	raw_spin_lock_irqsave(&lock->wait_lock, flags);
 	debug_mutex_unlock(lock);
 	if (!list_empty(&lock->wait_list)) {
 		/* get the first entry from the wait-list: */
@@ -959,7 +961,7 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
 		__mutex_handoff(lock, next);
 
 	preempt_disable();
-	raw_spin_unlock(&lock->wait_lock);
+	raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
 	wake_up_q(&wake_q);
 	preempt_enable();
 }

kernel/locking/ww_mutex.h

@@ -70,14 +70,14 @@ __ww_mutex_has_waiters(struct mutex *lock)
 	return atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS;
 }
 
-static inline void lock_wait_lock(struct mutex *lock)
+static inline void lock_wait_lock(struct mutex *lock, unsigned long *flags)
 {
-	raw_spin_lock(&lock->wait_lock);
+	raw_spin_lock_irqsave(&lock->wait_lock, *flags);
 }
 
-static inline void unlock_wait_lock(struct mutex *lock)
+static inline void unlock_wait_lock(struct mutex *lock, unsigned long *flags)
 {
-	raw_spin_unlock(&lock->wait_lock);
+	raw_spin_unlock_irqrestore(&lock->wait_lock, *flags);
 }
 
 static inline void lockdep_assert_wait_lock_held(struct mutex *lock)
@@ -144,14 +144,14 @@ __ww_mutex_has_waiters(struct rt_mutex *lock)
 	return rt_mutex_has_waiters(&lock->rtmutex);
 }
 
-static inline void lock_wait_lock(struct rt_mutex *lock)
+static inline void lock_wait_lock(struct rt_mutex *lock, unsigned long *flags)
 {
-	raw_spin_lock(&lock->rtmutex.wait_lock);
+	raw_spin_lock_irqsave(&lock->rtmutex.wait_lock, *flags);
 }
 
-static inline void unlock_wait_lock(struct rt_mutex *lock)
+static inline void unlock_wait_lock(struct rt_mutex *lock, unsigned long *flags)
 {
-	raw_spin_unlock(&lock->rtmutex.wait_lock);
+	raw_spin_unlock_irqrestore(&lock->rtmutex.wait_lock, *flags);
 }
 
 static inline void lockdep_assert_wait_lock_held(struct rt_mutex *lock)
@@ -380,6 +380,7 @@ static __always_inline void
 ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
 	DEFINE_WAKE_Q(wake_q);
+	unsigned long flags;
 
 	ww_mutex_lock_acquired(lock, ctx);
 
@@ -408,10 +409,10 @@ ww_mutex_set_context_fastpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 	 * Uh oh, we raced in fastpath, check if any of the waiters need to
 	 * die or wound us.
 	 */
-	lock_wait_lock(&lock->base);
+	lock_wait_lock(&lock->base, &flags);
 	__ww_mutex_check_waiters(&lock->base, ctx, &wake_q);
 	preempt_disable();
-	unlock_wait_lock(&lock->base);
+	unlock_wait_lock(&lock->base, &flags);
 	wake_up_q(&wake_q);
 	preempt_enable();
 }