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| author | Oleg Nesterov <oleg@redhat.com> | 2015-07-21 17:45:57 +0200 |
|---|---|---|
| committer | Oleg Nesterov <oleg@redhat.com> | 2015-08-15 13:52:10 +0200 |
| commit | 9287f6925ad9d8fb8c6283066b4f77fd87f123a9 (patch) | |
| tree | 45da8cd0ac42defea9ca9e1efee0dc6daf4189b4 | |
| parent | 0e28e01f1e73015d8e1b8fa1cda071d0bd9a2600 (diff) | |
| download | linux-rt-9287f6925ad9d8fb8c6283066b4f77fd87f123a9.tar.gz | |
percpu-rwsem: introduce percpu_down_read_trylock()
Add percpu_down_read_trylock(), it will have the user soon.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
| -rw-r--r-- | include/linux/percpu-rwsem.h | 1 | ||||
| -rw-r--r-- | kernel/locking/percpu-rwsem.c | 13 |
2 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 3e88c9a7d57f..16c30cd33501 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -16,6 +16,7 @@ struct percpu_rw_semaphore { }; extern void percpu_down_read(struct percpu_rw_semaphore *); +extern int percpu_down_read_trylock(struct percpu_rw_semaphore *); extern void percpu_up_read(struct percpu_rw_semaphore *); extern void percpu_down_write(struct percpu_rw_semaphore *); diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 652a8ee8efe9..f32567254867 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_); |