From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH 1/2 v3] wait: add wait_event_lock_irq() interface Date: Fri, 30 Nov 2012 13:43:53 -0800 Message-ID: <20121130134353.eb4ba17e.akpm@linux-foundation.org> References: <1354272161-9173-1-git-send-email-lczerner@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1354272161-9173-1-git-send-email-lczerner@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Lukas Czerner Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, axboe@kernel.dk, jmoyer@redhat.com, Neil Brown , David Howells , Ingo Molnar , Peter Zijlstra List-Id: linux-raid.ids On Fri, 30 Nov 2012 11:42:40 +0100 Lukas Czerner 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 > Cc: Neil Brown > Cc: David Howells > Cc: Ingo Molnar > Cc: Peter Zijlstra > --- > 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 _