[Xen-changelog] [xen master] rwlock: allow arch to override write_unlock() atomic

[patchbot@xxxxxxx]

commit 3a76bf0ea622e233cad1f871901eb25e4b40ec3f
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Jan 9 17:31:45 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jan 9 17:31:45 2015 +0100

    rwlock: allow arch to override write_unlock() atomic
    
    ... (for consistency with read_unlock()), and default it to xchg(),
    being generally cheaper than cmpxchg().
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Tim Deegan <tim@xxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/spinlock.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
index f6925ec..5fd8b1c 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -438,10 +438,14 @@ int _write_trylock(rwlock_t *lock)
     return 1;
 }
 
-void _write_unlock(rwlock_t *lock)
+#ifndef _raw_write_unlock
+# define _raw_write_unlock(l) xchg(&(l)->lock, 0)
+#endif
+
+inline void _write_unlock(rwlock_t *lock)
 {
     preempt_enable();
-    if ( cmpxchg(&lock->lock, RW_WRITE_FLAG, 0) != RW_WRITE_FLAG )
+    if ( _raw_write_unlock(lock) != RW_WRITE_FLAG )
         BUG();
 }
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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