ANDROID: vendor_hooks: add hooks in rwsem read trylock

When the lock is owned by readers and there is no RWSEM_FLAG_HANDOFF set,
we allow some specific new readers to acquire the lock immediately
in this hook, event if there are some writer tasks in the wait_list.
This features can optimize the priority inversion problem caused by
rwsem and improve system responsiveness and
performance.

Bug: 336506800

Change-Id: I7e8fded73579933d1f61faa9fb6e5f300ffd71bf
Signed-off-by: zhujingpeng <zhujingpeng@vivo.com>
[jstultz: rebased, resolved collision]
Signed-off-by: John Stultz <jstultz@google.com>
(cherry picked from commit ace91cdf950654038d449745d8218b2b3eb91017)

drivers/android/vendor_hooks.c

@@ -495,3 +495,4 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_record_rwsem_reader_owned);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_clear_rwsem_reader_owned);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_record_rwsem_writer_owned);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_clear_rwsem_writer_owned);
+EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_rwsem_read_trylock_failed);

include/trace/hooks/rwsem.h

@@ -44,6 +44,9 @@ DECLARE_HOOK(android_vh_record_rwsem_writer_owned,
 DECLARE_HOOK(android_vh_clear_rwsem_writer_owned,
 	TP_PROTO(struct rw_semaphore *sem),
 	TP_ARGS(sem));
+DECLARE_HOOK(android_vh_rwsem_read_trylock_failed,
+	TP_PROTO(struct rw_semaphore *sem, long *cntp, int *ret),
+	TP_ARGS(sem, cntp, ret));
 #endif /* _TRACE_HOOK_RWSEM_H */
 /* This part must be outside protection */
 #include <trace/define_trace.h>

kernel/locking/rwsem.c

@@ -254,6 +254,8 @@ static inline void rwsem_set_nonspinnable(struct rw_semaphore *sem)
 
 static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
 {
+	int ret = 0;
+
 	*cntp = atomic_long_add_return_acquire(RWSEM_READER_BIAS, &sem->count);
 
 	if (WARN_ON_ONCE(*cntp < 0))
@@ -265,6 +267,13 @@ static inline bool rwsem_read_trylock(struct rw_semaphore *sem, long *cntp)
 		return true;
 	}
 
+	trace_android_vh_rwsem_read_trylock_failed(sem, cntp, &ret);
+	if (ret) {
+		rwsem_set_reader_owned(sem);
+		trace_android_vh_record_rwsem_lock_starttime(sem, jiffies);
+		return true;
+	}
+
 	return false;
 }
 
@@ -1337,6 +1346,15 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
 			break;
 		}
 	}
+
+	if (!ret) {
+		trace_android_vh_rwsem_read_trylock_failed(sem, NULL, &ret);
+		if (ret) {
+			rwsem_set_reader_owned(sem);
+			trace_android_vh_record_rwsem_lock_starttime(sem, jiffies);
+		}
+	}
+
 	preempt_enable();
 	return ret;
 }