diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2019-10-30 20:30:41 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-02-11 13:10:56 +0100 |
| commit | 7f26482a872c36b2ee87ea95b9dcd96e3d5805df (patch) | |
| tree | 0a0e843a50333cc34780860e3378ecae2c5a52bf /kernel/locking/rwsem.c | |
| parent | 75ff64572e497578e238fefbdff221c96f29067a (diff) | |
locking/percpu-rwsem: Remove the embedded rwsem
The filesystem freezer uses percpu-rwsem in a way that is effectively
write_non_owner() and achieves this with a few horrible hacks that
rely on the rwsem (!percpu) implementation.
When PREEMPT_RT replaces the rwsem implementation with a PI aware
variant this comes apart.
Remove the embedded rwsem and implement it using a waitqueue and an
atomic_t.
- make readers_block an atomic, and use it, with the waitqueue
for a blocking test-and-set write-side.
- have the read-side wait for the 'lock' state to clear.
Have the waiters use FIFO queueing and mark them (reader/writer) with
a new WQ_FLAG. Use a custom wake_function to wake either a single
writer or all readers until a writer.
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/20200204092403.GB14879@hirez.programming.kicks-ass.net
Diffstat (limited to 'kernel/locking/rwsem.c')
| -rw-r--r-- | kernel/locking/rwsem.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index 30df8dff217b..81c0d75d5dab 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -28,7 +28,6 @@ #include <linux/rwsem.h> #include <linux/atomic.h> -#include "rwsem.h" #include "lock_events.h" /* @@ -1338,7 +1337,7 @@ static struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem) /* * lock for reading */ -inline void __down_read(struct rw_semaphore *sem) +static inline void __down_read(struct rw_semaphore *sem) { if (!rwsem_read_trylock(sem)) { rwsem_down_read_slowpath(sem, TASK_UNINTERRUPTIBLE); @@ -1383,7 +1382,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) /* * lock for writing */ -inline void __down_write(struct rw_semaphore *sem) +static inline void __down_write(struct rw_semaphore *sem) { long tmp = RWSEM_UNLOCKED_VALUE; @@ -1426,7 +1425,7 @@ static inline int __down_write_trylock(struct rw_semaphore *sem) /* * unlock after reading */ -inline void __up_read(struct rw_semaphore *sem) +static inline void __up_read(struct rw_semaphore *sem) { long tmp; @@ -1446,7 +1445,7 @@ inline void __up_read(struct rw_semaphore *sem) /* * unlock after writing */ -inline void __up_write(struct rw_semaphore *sem) +static inline void __up_write(struct rw_semaphore *sem) { long tmp; |