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authorHou Tao <houtao1@huawei.com>2020-09-15 17:07:50 +0300
committerPeter Zijlstra <peterz@infradead.org>2020-09-16 17:26:56 +0300
commite6b1a44eccfcab5e5e280be376f65478c3b2c7a2 (patch)
tree2175cb1bc02e8b795a2ebb5d3fe5263539e5cb4f /kernel
parent23870f1227680d2aacff6f79c3ab2222bd04e86e (diff)
downloadlinux-e6b1a44eccfcab5e5e280be376f65478c3b2c7a2.tar.xz
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 'kernel')
-rw-r--r--kernel/locking/percpu-rwsem.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 8bbafe3e5203..70a32a576f3f 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -45,7 +45,7 @@ EXPORT_SYMBOL_GPL(percpu_free_rwsem);
static bool __percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
{
- __this_cpu_inc(*sem->read_count);
+ this_cpu_inc(*sem->read_count);
/*
* Due to having preemption disabled the decrement happens on
@@ -71,7 +71,7 @@ static bool __percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
if (likely(!atomic_read_acquire(&sem->block)))
return true;
- __this_cpu_dec(*sem->read_count);
+ this_cpu_dec(*sem->read_count);
/* Prod writer to re-evaluate readers_active_check() */
rcuwait_wake_up(&sem->writer);