The following commit has been merged into the locking/core branch of tip: Commit-ID: 75ff64572e497578e238fefbdff221c96f29067a Gitweb: https://git.kernel.org/tip/75ff64572e497578e238fefbdff221c96f29067a Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Thu, 31 Oct 2019 12:34:23 +01:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Tue, 11 Feb 2020 13:10:55 +01:00 locking/percpu-rwsem: Extract __percpu_down_read_trylock() In preparation for removing the embedded rwsem and building a custom lock, extract the read-trylock primitive. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Reviewed-by: Davidlohr Bueso <dbueso@xxxxxxx> Acked-by: Will Deacon <will@xxxxxxxxxx> Acked-by: Waiman Long <longman@xxxxxxxxxx> Tested-by: Juri Lelli <juri.lelli@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200131151540.098485539@xxxxxxxxxxxxx --- kernel/locking/percpu-rwsem.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index becf925..b155e8e 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -45,7 +45,7 @@ void percpu_free_rwsem(struct percpu_rw_semaphore *sem) } EXPORT_SYMBOL_GPL(percpu_free_rwsem); -bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try) +static bool __percpu_down_read_trylock(struct percpu_rw_semaphore *sem) { __this_cpu_inc(*sem->read_count); @@ -73,11 +73,18 @@ bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try) if (likely(!smp_load_acquire(&sem->readers_block))) return true; - /* - * Per the above comment; we still have preemption disabled and - * will thus decrement on the same CPU as we incremented. - */ - __percpu_up_read(sem); + __this_cpu_dec(*sem->read_count); + + /* Prod writer to re-evaluate readers_active_check() */ + rcuwait_wake_up(&sem->writer); + + return false; +} + +bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try) +{ + if (__percpu_down_read_trylock(sem)) + return true; if (try) return false;
![]() |