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authorWill Deacon <will.deacon@arm.com>2017-10-12 15:20:49 +0300
committerIngo Molnar <mingo@kernel.org>2017-10-25 11:57:24 +0300
commitb519b56e378ee82caf9b079b04f5db87dedc3251 (patch)
tree82dddca8c324c5a32ef4a41945f625868ff7a03a /include/asm-generic
parent4df714be4dcf40bfb0d4af0f851a6e1977afa02e (diff)
downloadlinux-b519b56e378ee82caf9b079b04f5db87dedc3251.tar.xz
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.h4
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);
}
/**