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locking/qrwlock: Fix write unlock bug on big endian systems 

This patch aims to get rid of endianness in queued_write_unlock(). We
want to set  __qrwlock->wmode to NULL, however the address is not
&lock->cnts in big endian machine. That causes queued_write_unlock()
write NULL to the wrong field of __qrwlock.

So implement __qrwlock_write_byte() which returns the correct
__qrwlock->wmode address.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman.Long@hpe.com
Cc: arnd@arndb.de
Cc: boqun.feng@gmail.com
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1468835259-4486-1-git-send-email-xinhui.pan@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
pan xinhui 2016-07-18 17:47:39 +08:00 committed by Ingo Molnar
parent a2071cd765
commit 2db34e8bf9
1 changed files with 25 additions and 2 deletions
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27
include/asm-generic/qrwlock.h
View File

@ -25,7 +25,20 @@
#include <asm-generic/qrwlock_types.h>
/*
* Writer states & reader shift and bias
* Writer states & reader shift and bias.
*
* | +0 | +1 | +2 | +3 |
* ----+----+----+----+----+
* LE | 78 | 56 | 34 | 12 | 0x12345678
* ----+----+----+----+----+
* | wr | rd |
* +----+----+----+----+
*
* ----+----+----+----+----+
* BE | 12 | 34 | 56 | 78 | 0x12345678
* ----+----+----+----+----+
* | rd | wr |
* +----+----+----+----+
*/
#define _QW_WAITING 1 /* A writer is waiting */
#define _QW_LOCKED 0xff /* A writer holds the lock */
@ -133,13 +146,23 @@ static inline void queued_read_unlock(struct qrwlock *lock)
(void)atomic_sub_return_release(_QR_BIAS, &lock->cnts);
}
/**
* __qrwlock_write_byte - retrieve the write byte address of a queue rwlock
* @lock : Pointer to queue rwlock structure
* Return: the write byte address of a queue rwlock
*/
static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
{
return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
}
/**
* queued_write_unlock - release write lock of a queue rwlock
* @lock : Pointer to queue rwlock structure
*/
static inline void queued_write_unlock(struct qrwlock *lock)
{
smp_store_release((u8 *)&lock->cnts, 0);
smp_store_release(__qrwlock_write_byte(lock), 0);
}
/*