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From: Cyril Hrubis <chrubis@suse.cz>
To: Petr Vorel <pvorel@suse.cz>
Cc: linux-block@vger.kernel.org, Martijn Coenen <maco@android.com>,
	Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	ltp@lists.linux.it
Subject: Re: Ocassional dropping of uevent of loop device (possible race)
Date: Tue, 27 Oct 2020 20:25:50 +0100	[thread overview]
Message-ID: <20201027192550.GA28057@yuki.lan> (raw)
In-Reply-To: <20201027184926.GA24024@dell5510>

Hi!
> commit 716ad0986cbd ("loop: Switch to set_capacity_revalidate_and_notify()")
> from v5.8-rc1 caused occasional dropping of uevent of attached or detached loop
> device (not sure which one). The only difference is that
> set_capacity_revalidate_and_notify() has condition:
> if (capacity != size && capacity != 0 && size != 0)
> thus notification is not triggered here but in a different part of code.
> 
> It was found with LTP test uevent01 [1]:
> 
> # i=0; while true; do i=$((i+1)); echo "== $i =="; rmmod -f loop; ./uevent01 || break; done
> 
> It looks to be a race. Usually ~ 10 loops is enough.

Looks like the link to test source is missing and should have been:

[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/uevents/uevent01.c

-- 
Cyril Hrubis
chrubis@suse.cz

WARNING: multiple messages have this Message-ID (diff)
From: Cyril Hrubis <chrubis@suse.cz>
To: ltp@lists.linux.it
Subject: [LTP] Ocassional dropping of uevent of loop device (possible race)
Date: Tue, 27 Oct 2020 20:25:50 +0100	[thread overview]
Message-ID: <20201027192550.GA28057@yuki.lan> (raw)
In-Reply-To: <20201027184926.GA24024@dell5510>

Hi!
> commit 716ad0986cbd ("loop: Switch to set_capacity_revalidate_and_notify()")
> from v5.8-rc1 caused occasional dropping of uevent of attached or detached loop
> device (not sure which one). The only difference is that
> set_capacity_revalidate_and_notify() has condition:
> if (capacity != size && capacity != 0 && size != 0)
> thus notification is not triggered here but in a different part of code.
> 
> It was found with LTP test uevent01 [1]:
> 
> # i=0; while true; do i=$((i+1)); echo "== $i =="; rmmod -f loop; ./uevent01 || break; done
> 
> It looks to be a race. Usually ~ 10 loops is enough.

Looks like the link to test source is missing and should have been:

[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/uevents/uevent01.c

-- 
Cyril Hrubis
chrubis@suse.cz

  reply	other threads:[~2020-10-27 19:26 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-27 18:49 Ocassional dropping of uevent of loop device (possible race) Petr Vorel
2020-10-27 18:49 ` [LTP] " Petr Vorel
2020-10-27 19:25 ` Cyril Hrubis [this message]
2020-10-27 19:25   ` Cyril Hrubis

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