From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org,
peter@hurleysoftware.com, rjw@rjwysocki.net,
torvalds@linux-foundation.org, tglx@linutronix.de,
eparis@redhat.com, umgwanakikbuti@gmail.com, marcel@holtmann.org,
ebiederm@xmission.com, davem@davemloft.net,
fengguang.wu@intel.com
Subject: Re: [PATCH 2/7] wait: Reimplement wait_event_freezable()
Date: Fri, 31 Oct 2014 22:48:36 +0100 [thread overview]
Message-ID: <20141031214836.GQ10501@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20141031213802.GA25881@redhat.com>
On Fri, Oct 31, 2014 at 10:38:02PM +0100, Oleg Nesterov wrote:
> On 10/31, Peter Zijlstra wrote:
> >
> > Provide better implementations of wait_event_freezable() APIs.
> >
> > The problem is with freezer_do_not_count(), it hides the thread from
> > the freezer, even though this thread might not actually freeze/sleep
> > at all.
>
> I agree, wait_event_freezable() is awful. But could you clarify "at all" ?
>
> Sure, the task can be preempted right after it sets, it can do a lot
> of things before it calls schedule(), it can be woken after that and
> it can run again and do something else before freezer_count() calls
> try_to_freeze(), etc.
>
> Is this what you meant?
Yes.
> > +#define __wait_event_freezable(wq, condition) \
> > + (void)___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0, \
> > + schedule(); try_to_freeze())
>
> I don't think this can work.
Yeah, that was horribly broken. defconfig didn't seem to find a usage
site. Wu's robot offered a .config quickly enough though ;-)
next prev parent reply other threads:[~2014-10-31 21:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-31 11:10 [PATCH 0/7] Various fixes for nested sleep stuff Peter Zijlstra
2014-10-31 11:10 ` [PATCH 1/7] sched,wait: Fix a kthread race with wait_woken() Peter Zijlstra
2014-10-31 22:13 ` Oleg Nesterov
2014-10-31 11:10 ` [PATCH 2/7] wait: Reimplement wait_event_freezable() Peter Zijlstra
2014-10-31 17:41 ` Peter Zijlstra
2014-10-31 21:38 ` Oleg Nesterov
2014-10-31 21:48 ` Peter Zijlstra [this message]
2014-10-31 21:53 ` Oleg Nesterov
2014-10-31 11:10 ` [PATCH 3/7] wait: Remove wait_event_freezekillable() Peter Zijlstra
2014-10-31 11:10 ` [PATCH 4/7] audit,wait: Fixup kauditd_thread wait loop Peter Zijlstra
2014-10-31 11:10 ` [PATCH 5/7] rfcomm: Fix broken wait construct Peter Zijlstra
2014-10-31 11:10 ` [PATCH 6/7] netdev: Fix sleeping inside wait event Peter Zijlstra
2014-10-31 11:10 ` [PATCH 7/7] sched: Use WARN_ONCE for the might_sleep() TASK_RUNNING test Peter Zijlstra
2014-10-31 22:42 ` Oleg Nesterov
2014-11-03 7:56 ` Peter Zijlstra
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