On Fri, 30 Nov 2012 11:42:40 +0100
Lukas Czerner <lczerner@xxxxxxxxxx> wrote:
> New wait_event{_interruptible}_lock_irq{_cmd} macros added. This commit
> moves the private wait_event_lock_irq() macro from MD to regular wait
> includes, introduces new macro wait_event_lock_irq_cmd() instead of using
> the old method with omitting cmd parameter which is ugly and makes a use
> of new macros in the MD. It also introduces the _interruptible_ variant.
>
> The use of new interface is when one have a special lock to protect data
> structures used in the condition, or one also needs to invoke "cmd"
> before putting it to sleep.
>
> All new macros are expected to be called with the lock taken. The lock
> is released before sleep and is reacquired afterwards. We will leave the
> macro with the lock held.
>
> Note to DM: IMO this should also fix theoretical race on waitqueue while
> using simultaneously wait_event_lock_irq() and wait_event() because of
> lack of locking around current state setting and wait queue removal.
>
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> Cc: Neil Brown <neilb@xxxxxxx>
> Cc: David Howells <dhowells@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> ---
> v2: add interruptible variant, swap cmd and schedule, use prepare_to_wait
> v3: swap cmd and schedule so we call cmd before schedule
Your v3 patch reverts
http://ozlabs.org/~akpm/mmots/broken-out/wait-add-wait_event_lock_irq-interface-fix.patch.
Here's what I've queued in -mm:
--- a/include/linux/wait.h~wait-add-wait_event_lock_irq-interface-v3
+++ a/include/linux/wait.h
@@ -555,14 +555,13 @@ do { \
do { \
DEFINE_WAIT(__wait); \
\
- cmd; \
for (;;) { \
prepare_to_wait(&wq, &__wait, TASK_UNINTERRUPTIBLE); \
if (condition) \
break; \
spin_unlock_irq(&lock); \
- schedule(); \
cmd; \
+ schedule(); \
spin_lock_irq(&lock); \
} \
finish_wait(&wq, &__wait); \
@@ -575,8 +574,8 @@ do { \
* taken.
* @wq: the waitqueue to wait on
* @condition: a C expression for the event to wait for
- * @lock: a locked spinlock_t, which will be released before schedule()
- * and cmd reacquired afterwards.
+ * @lock: a locked spinlock_t, which will be released before cmd
+ * and schedule() and reacquired afterwards.
* @cmd: a command which is invoked outside the critical section before
* sleep
*
@@ -588,7 +587,7 @@ do { \
* change the result of the wait condition.
*
* This is supposed to be called while holding the lock. The lock is
- * dropped before going to sleep and invoking the cmd and is reacquired
+ * dropped before invoking the cmd and going to sleep and is reacquired
* afterwards.
*/
#define wait_event_lock_irq_cmd(wq, condition, lock, cmd) \
@@ -631,7 +630,6 @@ do { \
do { \
DEFINE_WAIT(__wait); \
\
- cmd; \
for (;;) { \
prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE); \
if (condition) \
@@ -641,8 +639,8 @@ do { \
break; \
} \
spin_unlock_irq(&lock); \
- schedule(); \
cmd; \
+ schedule(); \
spin_lock_irq(&lock); \
} \
finish_wait(&wq, &__wait); \
@@ -654,8 +652,8 @@ do { \
* be called with the lock taken.
* @wq: the waitqueue to wait on
* @condition: a C expression for the event to wait for
- * @lock: a locked spinlock_t, which will be released before schedule()
- * and cmd reacquired afterwards.
+ * @lock: a locked spinlock_t, which will be released before cmd and
+ * schedule() and reacquired afterwards.
* @cmd: a command which is invoked outside the critical section before
* sleep
*
@@ -667,7 +665,7 @@ do { \
* change the result of the wait condition.
*
* This is supposed to be called while holding the lock. The lock is
- * dropped before going to sleep and invoking the cmd and is reacquired
+ * dropped before invoking the cmd and going to sleep and is reacquired
* afterwards.
*
* The macro will return -ERESTARTSYS if it was interrupted by a signal
_
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