linux-kernel - [PATCH] locking/qrwlock: fix write unlock issue in big endian

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Message-Id: <1464862148-5672-1-git-send-email-xinhui.pan@linux.vnet.ibm.com>
Date:	Thu,  2 Jun 2016 18:09:08 +0800
From:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	arnd@...db.de, waiman.long@...com, peterz@...radead.org,
	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Subject: [PATCH] locking/qrwlock: fix write unlock issue in big endian

strcut __qrwlock has different layout in big endian machine. we need set
the __qrwlock->wmode to NULL, and the address is not &lock->cnts in big
endian machine.

Do as what read unlock does. we are lucky that the __qrwlock->wmode's
val is _QW_LOCKED.

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
---
 include/asm-generic/qrwlock.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 54a8e65..eadd7a3 100644
--- a/include/asm-generic/qrwlock.h
+++ b/include/asm-generic/qrwlock.h
@@ -139,7 +139,7 @@ static inline void queued_read_unlock(struct qrwlock *lock)
  */
 static inline void queued_write_unlock(struct qrwlock *lock)
 {
-	smp_store_release((u8 *)&lock->cnts, 0);
+	(void)atomic_sub_return_release(_QW_LOCKED, &lock->cnts);
 }
 
 /*
-- 
1.9.1