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author | Peter Zijlstra <peterz@infradead.org> | 2019-10-31 12:34:23 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2020-02-11 13:10:55 +0100 |
commit | 75ff64572e497578e238fefbdff221c96f29067a (patch) | |
tree | 1ad12e94e5eee534c451c298642444d79a4c082b | |
parent | 71365d40232110f7b029befc9033ea311d680611 (diff) | |
download | linux-75ff64572e497578e238fefbdff221c96f29067a.tar.bz2 |
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@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200131151540.098485539@infradead.org
-rw-r--r-- | kernel/locking/percpu-rwsem.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index becf925b27b5..b155e8e7ac39 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; |