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authorWaiman Long <longman@redhat.com>2021-04-26 20:50:17 +0200
committerPeter Zijlstra <peterz@infradead.org>2021-05-06 15:33:49 +0200
commit28ce0e70ecc30cc7d558a0304e6b816d70848f9a (patch)
treecf69b286807b78a02a43efbca299420f57cdef1b /kernel
parentsmp: Fix smp_call_function_single_async prototype (diff)
downloadlinux-28ce0e70ecc30cc7d558a0304e6b816d70848f9a.tar.xz
linux-28ce0e70ecc30cc7d558a0304e6b816d70848f9a.zip
locking/qrwlock: Cleanup queued_write_lock_slowpath()
Make the code more readable by replacing the atomic_cmpxchg_acquire() by an equivalent atomic_try_cmpxchg_acquire() and change atomic_add() to atomic_or(). For architectures that use qrwlock, I do not find one that has an atomic_add() defined but not an atomic_or(). I guess it should be fine by changing atomic_add() to atomic_or(). Note that the previous use of atomic_add() isn't wrong as only one writer that is the wait_lock owner can set the waiting flag and the flag will be cleared later on when acquiring the write lock. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lkml.kernel.org/r/20210426185017.19815-1-longman@redhat.com
Diffstat (limited to 'kernel')
-rw-r--r--kernel/locking/qrwlock.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
index b94f3831e963..ec36b73f4733 100644
--- a/kernel/locking/qrwlock.c
+++ b/kernel/locking/qrwlock.c
@@ -66,12 +66,12 @@ void queued_write_lock_slowpath(struct qrwlock *lock)
arch_spin_lock(&lock->wait_lock);
/* Try to acquire the lock directly if no reader is present */
- if (!atomic_read(&lock->cnts) &&
- (atomic_cmpxchg_acquire(&lock->cnts, 0, _QW_LOCKED) == 0))
+ if (!(cnts = atomic_read(&lock->cnts)) &&
+ atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED))
goto unlock;
/* Set the waiting flag to notify readers that a writer is pending */
- atomic_add(_QW_WAITING, &lock->cnts);
+ atomic_or(_QW_WAITING, &lock->cnts);
/* When no more readers or writers, set the locked flag */
do {