diff options
| author |   Will Deacon <will.deacon@arm.com> | 2017-10-12 13:20:49 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2017-10-25 10:57:24 +0200 |
| commit | b519b56e378ee82caf9b079b04f5db87dedc3251 (patch) | |
| tree | 82dddca8c324c5a32ef4a41945f625868ff7a03a /include/asm-generic | |
| parent | locking/atomic: Add atomic_cond_read_acquire() (diff) | |
| download | linux-dev-b519b56e378ee82caf9b079b04f5db87dedc3251.tar.xz linux-dev-b519b56e378ee82caf9b079b04f5db87dedc3251.zip | |
locking/qrwlock: Use atomic_cond_read_acquire() when spinning in qrwlock
The qrwlock slowpaths involve spinning when either a prospective reader
is waiting for a concurrent writer to drain, or a prospective writer is
waiting for concurrent readers to drain. In both of these situations,
atomic_cond_read_acquire() can be used to avoid busy-waiting and make use
of any backoff functionality provided by the architecture.
This patch replaces the open-code loops and rspin_until_writer_unlock()
implementation with atomic_cond_read_acquire(). The write mode transition
zero to _QW_WAITING is left alone, since (a) this doesn't need acquire
semantics and (b) should be fast.
Tested-by: Waiman Long <longman@redhat.com>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Tested-by: Adam Wallis <awallis@codeaurora.org>
Tested-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Jeremy.Linton@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1507810851-306-4-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/qrwlock.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h index 02c0a768e6b0..c716b02e8fd7 100644 --- a/include/asm-generic/qrwlock.h +++ b/include/asm-generic/qrwlock.h @@ -49,7 +49,7 @@ /* * External function declarations */ -extern void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts); +extern void queued_read_lock_slowpath(struct qrwlock *lock); extern void queued_write_lock_slowpath(struct qrwlock *lock); /** @@ -100,7 +100,7 @@ static inline void queued_read_lock(struct qrwlock *lock) return; /* The slowpath will decrement the reader count, if necessary. */ - queued_read_lock_slowpath(lock, cnts); + queued_read_lock_slowpath(lock); } /** |