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ANDROID: vendor_hook: Avoid clearing protect-flag before waking waiters

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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>
This commit is contained in:
xieliujie
2023-06-06 20:45:12 +08:00
committed by Liujie Xie
parent 2246168a72
commit 403d5d1318
3 changed files with 3 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/percpu-rwsem.h
View File

@@ -107,7 +107,6 @@ 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();
@@ -130,6 +129,7 @@ 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();
}

2
kernel/locking/mutex.c
View File

@@ -760,12 +760,12 @@ 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);

2
kernel/locking/percpu-rwsem.c
View File

@@ -258,7 +258,6 @@ 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_);
/*
@@ -284,6 +283,7 @@ 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);