From: Dmitry Maluka <D.Maluka@adbglobal.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Subject: Re: Yet another page fault deadlock
Date: Tue, 14 May 2013 18:38:02 +0300 [thread overview]
Message-ID: <kmtlsf$bjf$1@ger.gmane.org> (raw)
In-Reply-To: <CACVXFVNQVbe6MjWd9sH4wMK9fRCqxdvX2qSrep9GPfPPWOJ54A@mail.gmail.com>
Thanks for the remarks.
On 05/14/2013 01:32 PM, Ming Lei wrote:
> If the user buffer passed to driver A is mapped against file on the block
> device, single thread 1 may still deadlock on the mutex A.
Good point, thanks. It is unlikely to ever be a use case for us, but
still worth considering for the driver robustness.
> It can't be avoided 100% with the memset() workaround since the user
> buffer might be swapped out.
Yep. We have swap disabled though, so this should be fine as a temporary
workaround.
> Looks there are some similar examples, one of them is b31ca3f5df( sysfs:
> fix deadlock).
>
> ...
>
> Maybe it is good to document the lock usage, but the rule isn't much
> complicated: if one lock may be held under mmap_sem, the lock can't be
> held before copy_to/from_user(), :-)
Ok. I see it is a known pitfall. Still, it would be nice if people could
discover it not via a posteriori deadlocks debugging and lurking in list
archives. :)
prev parent reply other threads:[~2013-05-14 15:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-13 18:13 Dmitry Maluka
2013-05-14 10:32 ` Ming Lei
2013-05-14 15:38 ` Dmitry Maluka [this message]
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