From 57750518de5b7c167d41d352dc6b0d24c840cd76 Mon Sep 17 00:00:00 2001
From: xieliujie <xieliujie@oppo.com>
Date: Tue, 6 Jun 2023 20:45:12 +0800
Subject: [PATCH] ANDROID: vendor_hook: Avoid clearing protect-flag before
 waking waiters

With hooks below, we can mark a lock-owned thread with an identifiable flag, which can protect it from being preempted by some other unimportant threads, and then waiter will be wakeup more quickly.
https://android-review.googlesource.com/c/kernel/common/+/2183353

but now we find an issue like this one:
static inline void __up_write(struct rw_semaphore *sem)
{
        ...
        // Step 1. we clear flag.
        trace_android_vh_record_rwsem_lock_starttime(current, 0);
        // Step 2. owner may be preempted by unimportant threads.
        rwsem_clear_owner(sem);
        ...
        // Step 3. wake up waiter, but it's too later.
        if (unlikely(tmp & RWSEM_FLAG_WAITERS))
                rwsem_wake(sem);
}

This patch will clear protect-flag after waking up waiters.

Bug: 286024926
Change-Id: I71f8b6a7d8a01336fd36b8267c2cb5edab65bd11
Signed-off-by: xieliujie <xieliujie@oppo.com>
---
 include/linux/percpu-rwsem.h  | 2 +-
 kernel/locking/mutex.c        | 2 +-
 kernel/locking/percpu-rwsem.c | 2 +-
 kernel/locking/rwsem.c        | 4 ++--
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index 8a39613370a3..ebd81e03f3c1 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -102,7 +102,6 @@ static inline bool percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
 
 static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
 {
-	_trace_android_vh_record_pcpu_rwsem_starttime(current, 0);
 	rwsem_release(&sem->dep_map, _RET_IP_);
 
 	preempt_disable();
@@ -125,6 +124,7 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
 		this_cpu_dec(*sem->read_count);
 		rcuwait_wake_up(&sem->writer);
 	}
+	_trace_android_vh_record_pcpu_rwsem_starttime(current, 0);
 	preempt_enable();
 }
 
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index e2952e345bb1..4ff70da18e3c 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -555,12 +555,12 @@ static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigne
  */
 void __sched mutex_unlock(struct mutex *lock)
 {
-	trace_android_vh_record_mutex_lock_starttime(current, 0);
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
 	if (__mutex_unlock_fast(lock))
 		return;
 #endif
 	__mutex_unlock_slowpath(lock, _RET_IP_);
+	trace_android_vh_record_mutex_lock_starttime(current, 0);
 }
 EXPORT_SYMBOL(mutex_unlock);
 
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 2bf52ced2526..084aedde3d0f 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -269,7 +269,6 @@ EXPORT_SYMBOL_GPL(percpu_down_write);
 
 void percpu_up_write(struct percpu_rw_semaphore *sem)
 {
-	trace_android_vh_record_pcpu_rwsem_starttime(current, 0);
 	rwsem_release(&sem->dep_map, _RET_IP_);
 
 	/*
@@ -295,5 +294,6 @@ void percpu_up_write(struct percpu_rw_semaphore *sem)
 	 * exclusive write lock because its counting.
 	 */
 	rcu_sync_exit(&sem->rss);
+	trace_android_vh_record_pcpu_rwsem_starttime(current, 0);
 }
 EXPORT_SYMBOL_GPL(percpu_up_write);
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 257cbea27d65..1988ac0dc3b3 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1386,7 +1386,6 @@ static inline void __up_read(struct rw_semaphore *sem)
 	DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
 
 	preempt_disable();
-	trace_android_vh_record_rwsem_lock_starttime(current, 0);
 	rwsem_clear_reader_owned(sem);
 	tmp = atomic_long_add_return_release(-RWSEM_READER_BIAS, &sem->count);
 	DEBUG_RWSEMS_WARN_ON(tmp < 0, sem);
@@ -1395,6 +1394,7 @@ static inline void __up_read(struct rw_semaphore *sem)
 		clear_nonspinnable(sem);
 		rwsem_wake(sem);
 	}
+	trace_android_vh_record_rwsem_lock_starttime(current, 0);
 	preempt_enable();
 }
 
@@ -1414,12 +1414,12 @@ static inline void __up_write(struct rw_semaphore *sem)
 			    !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE), sem);
 
 	preempt_disable();
-	trace_android_vh_record_rwsem_lock_starttime(current, 0);
 	rwsem_clear_owner(sem);
 	tmp = atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count);
 	preempt_enable();
 	if (unlikely(tmp & RWSEM_FLAG_WAITERS))
 		rwsem_wake(sem);
+	trace_android_vh_record_rwsem_lock_starttime(current, 0);
 }
 
 /*