From: "Luis R. Rodriguez" <mcgrof-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: "Luis R. Rodriguez" <mcgrof-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
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linux-kernel
Subject: Re: [PATCH 0/4] firmware: fix fallback mechanism by ignoring SIGCHLD
Date: Mon, 26 Jun 2017 23:19:04 +0200 [thread overview]
Message-ID: <20170626211904.GD21846@wotan.suse.de> (raw)
In-Reply-To: <20170614222017.14653-1-mcgrof-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
On Wed, Jun 14, 2017 at 03:20:13PM -0700, Luis R. Rodriguez wrote:
> Martin reported an issue with Android where if sysfs is used to trigger a sync
> fw load which *relies* on the fallback mechanism and a background job completes
> while the trigger is ongoing in the foreground it will immediately fail the fw
> request. The issue can be observed in this simple test script using the
> test_firmware driver:
>
> set -e
> /etc/init.d/udev stop
> modprobe test_firmware
> DIR=/sys/devices/virtual/misc/test_firmware
> echo 10 >/sys/class/firmware/timeout
> sleep 2 &
> echo -n "does-not-exist-file.bin" > "$DIR"/trigger_request
>
> The background sleep triggers the SIGCHLD signal and we fail the firmware
> request on the fallback mechanism. This was due to the type of wait used which
> captures all signals, but we currently lack the killable swaits which would
> only allow killing the fallback wait on SIGKILL. This adds the missing killable
> swaits and fixes the firmware API to use it. This goes along with a test case to
> demo the issue clearly and how its fixed afterwards. Lastly, ensure to use
> -EINTR when interrupted so callers can distinguish between an interrupted
> failure and other types of failure.
>
> As suggested I've tagged the addition of the killable swaits and the firmware
> fix as stable. Between v4.0 and v4.10 the stable fix is to instead change
> the firmware to use wait_for_completion_killable_timeout() as the firmware
> API was only converted to swait as of v4.10.
>
> The last patch must be applied only after the killable wait is applied to
> ensure only SIGKILL triggers an interruption. Otherwise it has been observed
> using -EINTR on other signals like SIGCHLD will trigger a restart of the call,
> if a sysfs write() is used to trigger the sync firmware request. This might be
> due what signal(7) says about using the SA_RESTART flag when write() is called,
> in such cases the call will be automatically restarted after the signal handler
> returns. The excemption here naturally seems to be on SIGKILL.
>
> Note that although I *feared* this might implicate any use of non-killable waits
> on other system calls, such as finit_module(), initial testing confirms this to
> not be the case. For instance replacing the echo with modprobe on a module
> which does the same on init does not present the same issues. This could be due
> to the special SA_RESTART flag case on write() as noted above and sysfs...
> however, its not perfectly clear yet to me.
>
> As usual these patches are on my linux-next git tree, they are on the
> 20170614-fw-fixes branch based on linux-next 20170614 [0].
>
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20170614-fw-fixes
Greg, *poke*
Luis
next prev parent reply other threads:[~2017-06-26 21:19 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-14 22:20 [PATCH 0/4] firmware: fix fallback mechanism by ignoring SIGCHLD Luis R. Rodriguez
2017-06-14 22:20 ` [PATCH 1/4] test_firmware: add test case for SIGCHLD on sync fallback Luis R. Rodriguez
2017-06-14 22:20 ` [PATCH 2/4] swait: add the missing killable swaits Luis R. Rodriguez
[not found] ` <20170614222017.14653-3-mcgrof-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2017-06-29 12:54 ` Greg KH
[not found] ` <20170629125402.GH26046-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-06-29 13:05 ` Thomas Gleixner
2017-06-29 13:35 ` Greg KH
2017-06-29 13:46 ` Thomas Gleixner
2017-06-29 16:13 ` Linus Torvalds
2017-06-29 16:31 ` Matthew Wilcox
2017-06-29 17:29 ` Luis R. Rodriguez
2017-06-29 17:40 ` Davidlohr Bueso
2017-06-29 17:57 ` Linus Torvalds
2017-06-29 18:33 ` Davidlohr Bueso
[not found] ` <20170629183339.GD3954-3dK4OQgjB4rH06JGZaSw0A@public.gmane.org>
2017-06-29 18:59 ` Linus Torvalds
[not found] ` <CA+55aFz8Mhx+A-g-5yOG-O1ZLRUR_fpeeA4iBNGH8EnDBZEdpA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-06-29 19:40 ` Luis R. Rodriguez
2017-06-29 19:44 ` Luis R. Rodriguez
[not found] ` <20170629194455.GR21846-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2017-06-29 20:58 ` Jakub Kicinski
2017-06-29 22:50 ` Luis R. Rodriguez
2017-06-29 22:53 ` Jakub Kicinski
2017-06-29 23:00 ` Luis R. Rodriguez
2017-06-29 23:06 ` Jakub Kicinski
[not found] ` <20170629225003.GU21846-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2017-07-12 21:33 ` Luis R. Rodriguez
[not found] ` <20170629194015.GQ21846-B4tOwbsTzaBolqkO4TVVkw@public.gmane.org>
2017-06-29 20:57 ` Linus Torvalds
2017-07-05 2:06 ` Davidlohr Bueso
[not found] ` <20170705020635.GD11168-3dK4OQgjB4rH06JGZaSw0A@public.gmane.org>
2017-07-07 19:58 ` Linus Torvalds
2017-07-07 22:27 ` Davidlohr Bueso
2017-07-07 22:48 ` Linus Torvalds
2017-06-29 19:15 ` Marcelo Tosatti
[not found] ` <20170629191506.GB12368-I4X2Mt4zSy4@public.gmane.org>
2017-06-30 4:03 ` Linus Torvalds
2017-06-30 11:55 ` Marcelo Tosatti
2017-06-30 11:57 ` Marcelo Tosatti
2017-06-30 17:30 ` Krister Johansen
2017-06-14 22:20 ` [PATCH 3/4] firmware: avoid invalid fallback aborts by using killable swait Luis R. Rodriguez
2017-06-14 22:20 ` [PATCH 4/4] firmware: send -EINTR on signal abort on fallback mechanism Luis R. Rodriguez
2017-06-15 7:49 ` [PATCH 0/4] firmware: fix fallback mechanism by ignoring SIGCHLD Martin Fuzzey
[not found] ` <20170614222017.14653-1-mcgrof-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2017-06-26 21:19 ` Luis R. Rodriguez [this message]
2017-06-29 15:14 ` Greg KH
[not found] ` <20170629151442.GA4880-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-06-29 17:29 ` Luis R. Rodriguez
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