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Date: Tue, 7 May 2013 14:28:04 +0200 From: Pavel Machek <pavel@....cz> To: Colin Cross <ccross@...roid.com> Cc: linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Mandeep Singh Baines <msb@...omium.org>, Oleg Nesterov <oleg@...hat.com>, linux-nfs@...r.kernel.org, linux-pm@...r.kernel.org, netdev@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Tejun Heo <tj@...nel.org>, Len Brown <len.brown@...el.com> Subject: Re: [PATCH v3 02/16] freezer: add unsafe versions of freezable helpers for CIFS On Mon 2013-05-06 16:50:07, Colin Cross wrote: > CIFS calls wait_event_freezekillable_unsafe with a VFS lock held, > which is unsafe and will cause lockdep warnings when 6aa9707 > "lockdep: check that no locks held at freeze time" is reapplied > (it was reverted in dbf520a). CIFS shouldn't be doing this, but > it has long-running syscalls that must hold a lock but also > shouldn't block suspend. Until CIFS freeze handling is rewritten > to use a signal to exit out of the critical section, add a new > wait_event_freezekillable_unsafe helper that will not run the > lockdep test when 6aa9707 is reapplied, and call it from CIFS. > > In practice the likley result of holding the lock while freezing > is that a second task blocked on the lock will never freeze, > aborting suspend, but it is possible to manufacture a case using > the cgroup freezer, the lock, and the suspend freezer to create > a deadlock. Silencing the lockdep warning here will allow > problems to be found in other drivers that may have a more > serious deadlock risk, and prevent new problems from being added. > > Signed-off-by: Colin Cross <ccross@...roid.com> Acked-by: Pavel Machek <pavel@....cz> -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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