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From: Martin Wilck <mwilck@suse.com>
To: Benjamin Marzinski <bmarzins@redhat.com>,
	device-mapper development <dm-devel@redhat.com>
Cc: Bart Van Assche <Bart.VanAssche@wdc.com>
Subject: Re: [PATCH v2 1/7] libmultipath: fix tur checker locking
Date: Fri, 09 Feb 2018 21:30:56 +0100	[thread overview]
Message-ID: <1518208256.2937.16.camel@suse.com> (raw)
In-Reply-To: <1518134167-15938-2-git-send-email-bmarzins@redhat.com>

On Thu, 2018-02-08 at 17:56 -0600, Benjamin Marzinski wrote:
> ct->running is now an atomic variable.  When the thread is started
> it is set to 1. When the checker wants to kill a thread, it
> atomically
> sets the value to 0 and reads the previous value.  If it was 1,
> the checker cancels the thread. If it was 0, the nothing needs to be
> done.  After the checker has dealt with the thread, it sets ct-
> >thread
> to NULL.
> 
> When the thread is done, it atomicalllys sets the value of ct-
> >running
> to 0 and reads the previous value. If it was 1, the thread just
> exits.
> If it was 0, then the checker is trying to cancel the thread, and so
> the thread calls pause(), which is a cancellation point.
> 

I'm missing one thing here. My poor brain is aching.

cleanup_func() can be entered in two ways: a) if the thread has been
cancelled and passed a cancellation point already, or b) if it exits
normally and calls pthread_cleanup_pop(). 
In case b), waiting for the cancellation request by calling pause()
makes sense to me. But in case a), the thread has already seen the
cancellation request - wouldn't calling pause() cause it to sleep
forever?

Martin

-- 
Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

  parent reply	other threads:[~2018-02-09 20:30 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-08 23:56 [PATCH v2 0/7] multipath: miscellaneous bug fixes Benjamin Marzinski
2018-02-08 23:56 ` [PATCH v2 1/7] libmultipath: fix tur checker locking Benjamin Marzinski
2018-02-09 16:15   ` Bart Van Assche
2018-02-09 17:26     ` Benjamin Marzinski
2018-02-09 17:42       ` Bart Van Assche
2018-02-09 20:30   ` Martin Wilck [this message]
2018-02-09 23:04     ` Benjamin Marzinski
2018-02-09 23:28       ` Martin Wilck
2018-02-09 23:36         ` Martin Wilck
2018-02-10  0:17           ` Benjamin Marzinski
2018-02-10 16:03             ` Martin Wilck
2018-02-10  0:36           ` Benjamin Marzinski
2018-02-10 16:11             ` Martin Wilck
2018-02-10 19:42               ` Martin Wilck
2018-02-12 18:44                 ` Benjamin Marzinski
2018-02-12 19:16                   ` Martin Wilck
2018-02-08 23:56 ` [PATCH v2 2/7] multipath: fix DEF_TIMEOUT use Benjamin Marzinski
2018-02-08 23:56 ` [PATCH v2 3/7] multipathd: remove coalesce_paths from ev_add_map Benjamin Marzinski
2018-02-12 20:30   ` Martin Wilck
2018-02-08 23:56 ` [PATCH v2 4/7] multipathd: remove unused configure parameter Benjamin Marzinski
2018-02-08 23:56 ` [PATCH v2 5/7] Fix set_no_path_retry() regression Benjamin Marzinski
2018-02-12 20:13   ` Martin Wilck
2018-02-08 23:56 ` [PATCH v2 6/7] multipathd: change spurious uevent msg priority Benjamin Marzinski
2018-02-08 23:56 ` [PATCH v2 7/7] multipath: print sysfs state in fast list mode Benjamin Marzinski
2018-02-12 20:33   ` Martin Wilck

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