From: Peter Zijlstra <peterz@infradead.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"David S. Miller" <davem@davemloft.net>,
Tony Luck <tony.luck@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
x86@kernel.org, linux-alpha@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org,
linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 03/11] locking, rwsem: introduce basis for down_write_killable
Date: Wed, 30 Mar 2016 15:25:49 +0200 [thread overview]
Message-ID: <20160330132549.GU3408@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1456750705-7141-4-git-send-email-mhocko@kernel.org>
On Mon, Feb 29, 2016 at 01:58:17PM +0100, Michal Hocko wrote:
> @@ -215,16 +216,34 @@ void __sched __down_write(struct rw_semaphore *sem)
> */
> if (sem->count == 0)
> break;
> - set_task_state(tsk, TASK_UNINTERRUPTIBLE);
> + set_task_state(tsk, state);
> raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
> schedule();
> + if (signal_pending_state(state, current)) {
> + ret = -EINTR;
> + raw_spin_lock_irqsave(&sem->wait_lock, flags);
> + goto out;
> + }
> raw_spin_lock_irqsave(&sem->wait_lock, flags);
> }
> /* got the lock */
> sem->count = -1;
> @@ -487,20 +488,38 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
> /* Block until there are no active lockers. */
> do {
> schedule();
> - set_current_state(TASK_UNINTERRUPTIBLE);
> + if (signal_pending_state(state, current)) {
> + raw_spin_lock_irq(&sem->wait_lock);
> + ret = ERR_PTR(-EINTR);
> + goto out;
> + }
> + set_current_state(state);
> } while ((count = sem->count) & RWSEM_ACTIVE_MASK);
>
> raw_spin_lock_irq(&sem->wait_lock);
> }
> __set_current_state(TASK_RUNNING);
Why is the signal_pending_state() test _after_ the call to schedule()
and before the 'trylock'.
__mutex_lock_common() has it before the call to schedule and after the
'trylock'.
The difference is that rwsem will now respond to the KILL and return
-EINTR even if the lock is available, whereas mutex will acquire it and
ignore the signal (for a little while longer).
Neither is wrong per se, but I feel all the locking primitives should
behave in a consistent manner in this regard.
next prev parent reply other threads:[~2016-03-30 13:26 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 12:58 [PATCH 0/11] introduce down_write_killable for rw_semaphore Michal Hocko
2016-02-29 12:58 ` [PATCH 01/11] locking, rwsem: get rid of __down_write_nested Michal Hocko
2016-02-29 12:58 ` [PATCH 02/11] locking, rwsem: drop explicit memory barriers Michal Hocko
2016-02-29 12:58 ` [PATCH 03/11] locking, rwsem: introduce basis for down_write_killable Michal Hocko
2016-03-30 13:25 ` Peter Zijlstra [this message]
2016-03-31 8:33 ` Michal Hocko
2016-03-31 8:44 ` Peter Zijlstra
2016-03-31 8:55 ` [PATCH] " Michal Hocko
2016-02-29 12:58 ` [PATCH 04/11] alpha, rwsem: provide __down_write_killable Michal Hocko
2016-02-29 12:58 ` [PATCH 05/11] ia64, " Michal Hocko
2016-02-29 12:58 ` [PATCH 06/11] s390, " Michal Hocko
2016-02-29 12:58 ` [PATCH 07/11] sh, " Michal Hocko
2016-02-29 12:58 ` [PATCH 08/11] sparc, " Michal Hocko
2016-02-29 12:58 ` [PATCH 09/11] xtensa, " Michal Hocko
2016-02-29 12:58 ` [PATCH 10/11] x86, " Michal Hocko
2016-02-29 12:58 ` [PATCH 11/11] locking, rwsem: provide down_write_killable Michal Hocko
2016-03-30 13:32 ` [PATCH 0/11] introduce down_write_killable for rw_semaphore Peter Zijlstra
2016-03-31 8:59 ` Michal Hocko
2016-03-31 9:20 ` Ingo Molnar
2016-03-31 10:58 ` Michal Hocko
2016-03-31 17:03 ` Andrew Morton
2016-04-01 6:33 ` Ingo Molnar
2016-04-01 9:21 ` Michal Hocko
2016-04-01 9:50 ` Ingo Molnar
2016-04-01 10:52 ` Michal Hocko
2016-04-01 7:26 ` Michal Hocko
2016-04-01 9:11 ` Andrew Morton
2016-04-01 11:04 [PATCH 0/11] introduce down_write_killable for rw_semaphore v2 Michal Hocko
2016-04-01 11:04 ` [PATCH 03/11] locking, rwsem: introduce basis for down_write_killable Michal Hocko
2016-04-02 4:41 ` Davidlohr Bueso
2016-04-04 9:17 ` Michal Hocko
2016-04-04 9:21 ` Peter Zijlstra
2016-04-07 6:58 ` Davidlohr Bueso
2016-04-07 7:38 ` Michal Hocko
2016-05-10 10:43 ` Tetsuo Handa
2016-05-10 11:53 ` Michal Hocko
2016-05-10 12:38 ` Peter Zijlstra
2016-05-10 13:57 ` Tetsuo Handa
2016-05-11 7:23 ` Michal Hocko
2016-05-11 8:28 ` Michal Hocko
2016-05-11 8:44 ` Peter Zijlstra
2016-05-11 9:04 ` Michal Hocko
2016-05-11 9:17 ` Peter Zijlstra
2016-05-11 9:31 ` Michal Hocko
2016-05-11 9:41 ` Peter Zijlstra
2016-05-11 13:59 ` Michal Hocko
2016-05-11 18:03 ` Michal Hocko
2016-05-12 12:12 ` Peter Zijlstra
2016-05-12 12:19 ` Michal Hocko
2016-05-12 13:58 ` Peter Zijlstra
2016-05-12 19:42 ` Waiman Long
2016-05-11 8:35 ` Peter Zijlstra
2016-05-11 9:02 ` Michal Hocko
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