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From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: WARNING: possible circular locking dependency detected
Date: Thu, 31 Aug 2017 10:09:22 +0200	[thread overview]
Message-ID: <20170831080922.daaypuxatenmpkfo@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.20.1708310952490.1874@nanos>

On Thu, Aug 31, 2017 at 09:55:57AM +0200, Thomas Gleixner wrote:
> > Arghh!!!
> > 
> > And allowing us to create events for offline CPUs (possible I think, but
> > maybe slightly tricky) won't solve that, because we're already holding
> > the hotplug_lock during PREPARE.
> 
> There are two ways to cure that:
> 
> 1) Have a pre cpus_write_lock() stage which is serialized via
>    cpus_add_remove_lock, which is the outer lock for hotplug.
> 
>    There we can sanely create stuff and fail with all consequences.

True, if you're willing to add more state to that hotplug thing I'll try
and make that perf patch that allows attaching to offline CPUs.

  reply	other threads:[~2017-08-31  8:09 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-25 10:03 WARNING: possible circular locking dependency detected Borislav Petkov
2017-08-25 11:45 ` Borislav Petkov
2017-08-25 14:47 ` Sebastian Andrzej Siewior
2017-08-25 16:12   ` Byungchul Park
2017-08-25 16:21     ` Thomas Gleixner
2017-08-28  7:41   ` Peter Zijlstra
2017-08-28 14:11   ` Peter Zijlstra
2017-08-29 19:34   ` Peter Zijlstra
2017-08-25 16:42 ` Sebastian Andrzej Siewior
2017-08-28 14:58 ` Peter Zijlstra
2017-08-28 15:06   ` Peter Zijlstra
2017-08-28 16:32     ` Peter Zijlstra
2017-08-29 17:40   ` Thomas Gleixner
2017-08-29 19:49     ` Peter Zijlstra
2017-08-29 20:10       ` Thomas Gleixner
2017-08-30  5:47         ` Peter Zijlstra
2017-08-31  7:08           ` Thomas Gleixner
2017-08-31  7:37             ` Peter Zijlstra
2017-08-31  7:55               ` Thomas Gleixner
2017-08-31  8:09                 ` Peter Zijlstra [this message]
2017-08-31  8:15                   ` Thomas Gleixner
2017-08-31 21:24                     ` Thomas Gleixner
2017-09-01 20:32                       ` Peter Zijlstra
2018-11-14  2:41 Qian Cai

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