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Date: Mon, 10 Oct 2016 08:54:55 +1100
From: Dave Chinner <david@fromorbit.com>
To: CAI Qian <caiqian@redhat.com>
Cc: Jan Kara <jack@suse.cz>, Miklos Szeredi <miklos@szeredi.hu>,
        tj <tj@kernel.org>, Al Viro <viro@ZenIV.linux.org.uk>,
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Subject: Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT]
 splice_read reworked)
Message-ID: <20161009215454.GM9806@dastard>
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On Fri, Oct 07, 2016 at 02:56:22PM -0400, CAI Qian wrote:
> 
> 
> ----- Original Message -----
> > From: "CAI Qian" <caiqian@redhat.com>
> > To: "Jan Kara" <jack@suse.cz>, "Miklos Szeredi" <miklos@szeredi.hu>, "tj" <tj@kernel.org>, "Al Viro"
> > <viro@ZenIV.linux.org.uk>, "Linus Torvalds" <torvalds@linux-foundation.org>, "Dave Chinner" <david@fromorbit.com>
> > Cc: "linux-xfs" <linux-xfs@vger.kernel.org>, "Jens Axboe" <axboe@kernel.dk>, "Nick Piggin" <npiggin@gmail.com>,
> > linux-fsdevel@vger.kernel.org, "Dave Jones" <davej@codemonkey.org.uk>
> > Sent: Friday, October 7, 2016 11:27:55 AM
> > Subject: Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked)
> > 
> > 
> > 
> > > Hmm, this round of trinity triggered a different hang.
> > This hang is reproducible so far with the command below on a overlayfs/xfs,
> Another data point is that this hang can also be reproduced using device-mapper thinp
> as the docker backend.

Again, no evidence that the system is actually hung. Waiting on
locks, yes, but nothing to indicate there is a deadlock in those
waiters.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com