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From: Srivatsa Vaddagiri <>
To: Christoph Lameter <>
Cc: Heiko Carstens <>,
	Benjamin Gilbert <>,, Ingo Molnar <>,
	Gautham shenoy <>, Andrew Morton <>,
	Pekka Enberg <>
Subject: Re: [patch -mm] slab: use CPU_LOCK_[ACQUIRE|RELEASE]
Date: Thu, 11 Jan 2007 08:00:05 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Jan 10, 2007 at 10:20:28AM -0800, Christoph Lameter wrote:
> I have got a bad feeling about upcoming deadlock problems when looking at
> the mutex_lock / unlock code in cpuup_callback in slab.c. Branches
> that just obtain a lock or release a lock? I hope there is some
> control of  what happens between lock acquisition and release?

A cpu hotplug should happen between LOCK_ACQUIRE/RELEASE

> You are aware that this lock is taken for cache shrinking/destroy, tuning
> of cpu cache sizes, proc output and cache creation? Any of those run on
> the same processor should cause a deadlock.

Why? mutex_lock() taken in LOCK_ACQ will just block those functions
(cache create etc) from proceeding simultaneously as a hotplug event.
This per-subsystem mutex_lock() is supposed to be a replacement for the global
lock_cpu_hotplug() lock .. 

But the whole thing is changing again ..we will likely move towards a
process freezer based cpu hotplug locking ..all the lock_cpu_hotplugs()
and the existing LOCK_ACQ/RELS can go away when we do that ..


  reply	other threads:[~2007-01-11  2:30 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-08 17:07 Failure to release lock after CPU hot-unplug canceled Benjamin Gilbert
2007-01-09 12:17 ` Heiko Carstens
2007-01-09 12:27   ` Srivatsa Vaddagiri
2007-01-09 15:03     ` Heiko Carstens
2007-01-09 15:05       ` [patch -mm] call cpu_chain with CPU_DOWN_FAILED if CPU_DOWN_PREPARE failed Heiko Carstens
2007-01-09 15:06       ` [patch -mm] slab: use CPU_LOCK_[ACQUIRE|RELEASE] Heiko Carstens
2007-01-10 18:20         ` Christoph Lameter
2007-01-11  2:30           ` Srivatsa Vaddagiri [this message]
2007-01-09 16:34       ` Failure to release lock after CPU hot-unplug canceled Benjamin Gilbert

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