From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
Sasha Levin <sasha.levin@oracle.com>,
Waiman Long <Waiman.Long@hp.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrey Ryabinin <a.ryabinin@samsung.com>,
Dave Jones <davej@codemonkey.org.uk>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: sched: memory corruption on completing completions
Date: Fri, 06 Feb 2015 12:18:22 +0530 [thread overview]
Message-ID: <54D463B6.2020808@linux.vnet.ibm.com> (raw)
In-Reply-To: <CA+55aFzL-TLA0SO1M0P8=SnK=ppANn4Uw2e_y+vV-SmjvkPt-g@mail.gmail.com>
On 02/06/2015 04:27 AM, Linus Torvalds wrote:
> On Thu, Feb 5, 2015 at 2:37 PM, Davidlohr Bueso <dave@stgolabs.net> wrote:
>>>
>>> It is possible that the paravirt spinlocks could be saved by:
>>>
>>> - moving the clearing of TICKET_SLOWPATH_FLAG into the fastpath locking code.
>>
>> Ouch, to avoid deadlocks they explicitly need the unlock to occur before
>> the slowpath tail flag is read.
>
> Well, just make the unlock do the actual real unlock operation
> ("fastpath"), leaving the TICKET_SLOWPATH_FLAG alone. The unlock path
> can *test* the flag and do whatever kicking it needs to get people
> started again, but not clear it again.
>
This is definitely a good idea, will think more on this.
(especially since any remote possibility of forgetting to wake up the
lock-waiter would result in eventual hang of kvm guest).
Hopeful to come up with a solution soon.
/me agreeing with the fact that we did not have the 'lifetime' in mind
during the design :(.
next prev parent reply other threads:[~2015-02-06 6:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-04 23:24 sched: memory corruption on completing completions Sasha Levin
2015-02-04 23:46 ` Andrew Morton
2015-02-05 0:16 ` Linus Torvalds
2015-02-05 7:10 ` Ingo Molnar
2015-02-05 9:30 ` Peter Zijlstra
2015-02-05 20:44 ` Sasha Levin
2015-02-05 20:59 ` Davidlohr Bueso
2015-02-05 21:02 ` Sasha Levin
2015-02-05 21:34 ` Linus Torvalds
2015-02-05 22:37 ` Davidlohr Bueso
2015-02-05 22:57 ` Linus Torvalds
2015-02-06 6:48 ` Raghavendra K T [this message]
2015-02-06 15:00 ` Raghavendra K T
2015-02-06 12:29 ` Raghavendra K T
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