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| author |   Hou Tao <houtao1@huawei.com> | 2020-09-15 22:07:50 +0800 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2020-09-16 16:26:56 +0200 |
| commit | e6b1a44eccfcab5e5e280be376f65478c3b2c7a2 (patch) | |
| tree | 2175cb1bc02e8b795a2ebb5d3fe5263539e5cb4f /include/linux/percpu-rwsem.h | |
| parent | locking/lockdep: Fix "USED" <- "IN-NMI" inversions (diff) | |
| download | wireguard-linux-e6b1a44eccfcab5e5e280be376f65478c3b2c7a2.tar.xz wireguard-linux-e6b1a44eccfcab5e5e280be376f65478c3b2c7a2.zip | |
locking/percpu-rwsem: Use this_cpu_{inc,dec}() for read_count
The __this_cpu*() accessors are (in general) IRQ-unsafe which, given
that percpu-rwsem is a blocking primitive, should be just fine.
However, file_end_write() is used from IRQ context and will cause
load-store issues on architectures where the per-cpu accessors are not
natively irq-safe.
Fix it by using the IRQ-safe this_cpu_*() for operations on
read_count. This will generate more expensive code on a number of
platforms, which might cause a performance regression for some of the
other percpu-rwsem users.
If any such is reported, we can consider alternative solutions.
Fixes: 70fe2f48152e ("aio: fix freeze protection of aio writes")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/20200915140750.137881-1-houtao1@huawei.com
Diffstat (limited to '')
| -rw-r--r-- | include/linux/percpu-rwsem.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 5e033fe1ff4e..5fda40f97fe9 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -60,7 +60,7 @@ static inline void percpu_down_read(struct percpu_rw_semaphore *sem) * anything we did within this RCU-sched read-size critical section. */ if (likely(rcu_sync_is_idle(&sem->rss))) - __this_cpu_inc(*sem->read_count); + this_cpu_inc(*sem->read_count); else __percpu_down_read(sem, false); /* Unconditional memory barrier */ /* @@ -79,7 +79,7 @@ static inline bool percpu_down_read_trylock(struct percpu_rw_semaphore *sem) * Same as in percpu_down_read(). */ if (likely(rcu_sync_is_idle(&sem->rss))) - __this_cpu_inc(*sem->read_count); + this_cpu_inc(*sem->read_count); else ret = __percpu_down_read(sem, true); /* Unconditional memory barrier */ preempt_enable(); @@ -103,7 +103,7 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem) * Same as in percpu_down_read(). */ if (likely(rcu_sync_is_idle(&sem->rss))) { - __this_cpu_dec(*sem->read_count); + this_cpu_dec(*sem->read_count); } else { /* * slowpath; reader will only ever wake a single blocked @@ -115,7 +115,7 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem) * aggregate zero, as that is the only time it matters) they * will also see our critical section. */ - __this_cpu_dec(*sem->read_count); + this_cpu_dec(*sem->read_count); rcuwait_wake_up(&sem->writer); } preempt_enable(); |