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Message-ID: <20120327154305.GA19314@redhat.com>
Date: Tue, 27 Mar 2012 17:43:05 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Boaz Harrosh <bharrosh@...asas.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
linux-security-module@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Turner <pjt@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
NFS list <linux-nfs@...r.kernel.org>,
Trond Myklebust <Trond.Myklebust@...app.com>,
"Bhamare, Sachin" <sbhamare@...asas.com>,
David Howells <dhowells@...hat.com>,
Eric Paris <eparis@...hat.com>,
"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
Kay Sievers <kay.sievers@...y.org>,
James Morris <jmorris@...ei.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Greg KH <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rjw@...k.pl>,
"keyrings@...ux-nfs.org" <keyrings@...ux-nfs.org>
Subject: Re: [PATCH 5/6] kmod: Add new call_usermodehelper_timeout() API
Hi Boaz,
I'll read this series tomorrow, but
On 03/26, Boaz Harrosh wrote:
>
> int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
> {
> DECLARE_COMPLETION_ONSTACK(done);
> + int wait_state;
> int retval = 0;
>
> helper_lock();
> @@ -540,19 +541,15 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
> if (wait == UMH_NO_WAIT) /* task has freed sub_info */
> goto unlock;
>
> - if (wait & UMH_KILLABLE) {
> - retval = wait_for_completion_killable(&done);
> - if (!retval)
> - goto wait_done;
> -
> + wait_state = (wait & UMH_KILLABLE) ? TASK_KILLABLE : 0;
> + retval = wait_for_completion_timeout_state(&done, sub_info->timeout,
> + wait_state);
> + if (unlikely(retval)) {
> /* umh_complete() will see NULL and free sub_info */
> if (xchg(&sub_info->complete, NULL))
> goto unlock;
> - /* fallthrough, umh_complete() was already called */
> }
>
> - wait_for_completion(&done);
at first glance this looks certainly wrong, or I misread the patch.
We can't remove the "fallback to wait_for_completion" logic until
you move the completion into subprocess_info (the next patch seems
to do this).
xchg() can race with umh_complete(). If it returns NULL, umh_complete()
was already called and got ->complete != NULL, we must not return until
umh_complete() finishes complete().
Oleg.
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