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-rw-r--r--kernel/locking/percpu-rwsem.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 652a8ee8e..f32567254 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -88,6 +88,19 @@ void percpu_down_read(struct percpu_rw_semaphore *brw)
__up_read(&brw->rw_sem);
}
+int percpu_down_read_trylock(struct percpu_rw_semaphore *brw)
+{
+ if (unlikely(!update_fast_ctr(brw, +1))) {
+ if (!__down_read_trylock(&brw->rw_sem))
+ return 0;
+ atomic_inc(&brw->slow_read_ctr);
+ __up_read(&brw->rw_sem);
+ }
+
+ rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 1, _RET_IP_);
+ return 1;
+}
+
void percpu_up_read(struct percpu_rw_semaphore *brw)
{
rwsem_release(&brw->rw_sem.dep_map, 1, _RET_IP_);