* [PATCH v4] locking/qrwlock: Fix write unlock issue in big endian
@ 2016-07-18 9:47 Pan Xinhui
2016-07-21 16:17 ` Will Deacon
2016-08-10 18:05 ` [tip:locking/core] locking/qrwlock: Fix write unlock bug on big endian systems tip-bot for pan xinhui
0 siblings, 2 replies; 3+ messages in thread
From: Pan Xinhui @ 2016-07-18 9:47 UTC (permalink / raw)
To: linux-kernel, linux-arch
Cc: peterz, arnd, Waiman.Long, mingo, will.deacon, boqun.feng, pan xinhui
From: pan xinhui <xinhui.pan@linux.vnet.ibm.com>
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>
---
change from v3:
rewrite totally. :)
change from v2:
change macro's name, add comments.
change from v1:
A typo fix which is really bad...
thanks Will for the carefull review.
---
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);
}
/*
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v4] locking/qrwlock: Fix write unlock issue in big endian
2016-07-18 9:47 [PATCH v4] locking/qrwlock: Fix write unlock issue in big endian Pan Xinhui
@ 2016-07-21 16:17 ` Will Deacon
2016-08-10 18:05 ` [tip:locking/core] locking/qrwlock: Fix write unlock bug on big endian systems tip-bot for pan xinhui
1 sibling, 0 replies; 3+ messages in thread
From: Will Deacon @ 2016-07-21 16:17 UTC (permalink / raw)
To: Pan Xinhui
Cc: linux-kernel, linux-arch, peterz, arnd, Waiman.Long, mingo, boqun.feng
On Mon, Jul 18, 2016 at 05:47:39PM +0800, Pan Xinhui wrote:
> From: pan xinhui <xinhui.pan@linux.vnet.ibm.com>
>
> 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>
> ---
> change from v3:
> rewrite totally. :)
> change from v2:
> change macro's name, add comments.
> change from v1:
> A typo fix which is really bad...
> thanks Will for the carefull review.
> ---
> 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);
> +}
Might be worth a comment here, saying that IS_BUILTIN expands to 1 or 0.
Either way, the patch looks correct to me:
Acked-by: Will Deacon <will.deacon@arm.com>
Will
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip:locking/core] locking/qrwlock: Fix write unlock bug on big endian systems
2016-07-18 9:47 [PATCH v4] locking/qrwlock: Fix write unlock issue in big endian Pan Xinhui
2016-07-21 16:17 ` Will Deacon
@ 2016-08-10 18:05 ` tip-bot for pan xinhui
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for pan xinhui @ 2016-08-10 18:05 UTC (permalink / raw)
To: linux-tip-commits
Cc: tglx, mingo, peterz, torvalds, xinhui.pan, akpm, paulmck,
linux-kernel, hpa
Commit-ID: 2db34e8bf9a22f4e38b29deccee57457bc0e7d74
Gitweb: http://git.kernel.org/tip/2db34e8bf9a22f4e38b29deccee57457bc0e7d74
Author: pan xinhui <xinhui.pan@linux.vnet.ibm.com>
AuthorDate: Mon, 18 Jul 2016 17:47:39 +0800
Committer: Ingo Molnar <mingo@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) <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>
---
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);
}
/*
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2016-07-18 9:47 [PATCH v4] locking/qrwlock: Fix write unlock issue in big endian Pan Xinhui
2016-07-21 16:17 ` Will Deacon
2016-08-10 18:05 ` [tip:locking/core] locking/qrwlock: Fix write unlock bug on big endian systems tip-bot for pan xinhui
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