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From: David Hildenbrand <>
To: "Paul E. McKenney" <>
Subject: Re: [PATCH v1] CPU hotplug: active_reader not woken up in some cases - deadlock
Date: Mon, 8 Dec 2014 20:30:18 +0100	[thread overview]
Message-ID: <20141208203018.24f23bdb@thinkpad-w530> (raw)
In-Reply-To: <>

> > active_writer is cleared while holding cpuhp_lock, so this should be safe,
> > right?
> You lost me on that one.  Don't we get to that piece of code precisely
> because we don't hold any of the CPU-hotplug locks?  If so, the
> writer might well hold all the locks it needs, and might well change
> cpu_hotplug.active_writer out from under us.
> What am I missing here?
> 							Thanx, Paul

I was missing that cpuhp_lock_* are simply lockdep anotations ... it's
getting late :)

So you're right, we need to verify that we don't get a 0 on the second access.

Will send an updated version soon.


  reply	other threads:[~2014-12-08 19:30 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-08 18:13 David Hildenbrand
2014-12-08 18:15 ` David Hildenbrand
2014-12-08 18:31 ` Paul E. McKenney
2014-12-08 18:58   ` David Hildenbrand
2014-12-08 19:08     ` Paul E. McKenney
2014-12-08 19:30       ` David Hildenbrand [this message]
2014-12-08 20:47         ` Paul E. McKenney

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