From: Al Viro <viro@ZenIV.linux.org.uk>
To: Vitaly Chernooky <vitalii.chernookyi@globallogic.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"David Vrabel" <david.vrabel@citrix.com>,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
"Iurii Konovalenko" <iurii.konovalenko@globallogic.com>,
"Ian Campbell" <ian.campbell@citrix.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Andrii Anisov" <andrii.anisov@globallogic.com>,
"Artem Mygaiev" <artem.mygaiev@globallogic.com>
Subject: Re: [PATCH] [RFC] Fix deadlock on regular nonseekable files
Date: Fri, 20 Mar 2015 14:46:34 +0000 [thread overview]
Message-ID: <20150320144634.GY29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CANZZXhBNSVmFTsteG7AAHuuYK7qU8J2LaHfcO16-2mcc+7kxag@mail.gmail.com>
On Fri, Mar 20, 2015 at 04:22:11PM +0200, Vitaly Chernooky wrote:
> > AFAICS, any threads blocked on f_pos_lock are not holding anything else and
> > cannot impede the rest. What am I missing here?
>
> As far as I understand it is true only for files on regular filesystem
> like ext4. Let's to see how XEN guys run into trouble with that
> f_pos_lock:
What does it have to do with filesystem type involved? The only place that
takes f_pos_lock is __fdget_pos(), with only one caller in the entire tree -
fdget_pos(). Which is static in fs/read_write.c and all its callers are
in right in the beginning of sys_<something>.
Is it just that they have read() on procfs file blocked waiting for something
and a bunch of other read/write on the same descriptor blocked on ->f_pos_mutex
waiting for that sucker to finish?
Then basically they are asking to waive XSI 2.9.7 for that file - behaviour
*is* required by POSIX.
What file it is and what is the first read() (or write(), whatever) blocked on?
Stack traces would be useful for the latter...
next prev parent reply other threads:[~2015-03-20 14:46 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-20 13:17 [PATCH] [RFC] Fix deadlock on regular nonseekable files Vitaly Chernooky
2015-03-20 13:42 ` Al Viro
2015-03-20 14:22 ` Vitaly Chernooky
2015-03-20 14:22 ` Vitaly Chernooky
2015-03-20 14:46 ` Al Viro [this message]
2015-03-20 17:37 ` Vitaly Chernooky
2015-03-20 17:55 ` Al Viro
2015-03-20 19:00 ` Marek Marczykowski-Górecki
2015-03-20 19:35 ` Al Viro
2015-03-20 19:35 ` Al Viro
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