Commit-ID: 2db34e8bf9a22f4e38b29deccee57457bc0e7d74 Gitweb: http://git.kernel.org/tip/2db34e8bf9a22f4e38b29deccee57457bc0e7d74 Author: pan xinhui <xinhui....@linux.vnet.ibm.com> AuthorDate: Mon, 18 Jul 2016 17:47:39 +0800 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 10 Aug 2016 14:13:27 +0200
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) <pet...@infradead.org> Signed-off-by: Pan Xinhui <xinhui....@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: waiman.l...@hpe.com Cc: a...@arndb.de Cc: boqun.f...@gmail.com Cc: will.dea...@arm.com Link: http://lkml.kernel.org/r/1468835259-4486-1-git-send-email-xinhui....@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- include/asm-generic/qrwlock.h | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h index 54a8e65..7d026bf 100644 --- a/include/asm-generic/qrwlock.h +++ b/include/asm-generic/qrwlock.h @@ -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 */ @@ -134,12 +147,22 @@ static inline void queued_read_unlock(struct qrwlock *lock) } /** + * __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); } /*
