When a new timer instance is created and assigned to the active link
in snd_timer_open(), the caller still doesn't (can't) set its callback
and callback data. In both the user-timer and the sequencer-timer
code, they do manually set up the callbacks after calling
snd_timer_open(). This has a potential risk of race when the timer
instance is added to the already running timer target, as the callback
might get triggered during setting up the callback itself.
This patch tries to address it by changing the API usage slightly:
- An empty timer instance is created at first via the new function
snd_timer_instance_new(). This object isn't linked to the timer
list yet.
- The caller sets up the callbacks and others stuff for the new timer
instance.
- The caller invokes snd_timer_open() with this instance, so that it's
linked to the target timer.
For closing, do similarly:
- Call snd_timer_close(). This unlinks the timer instance from the
timer list.
- Free the timer instance via snd_timer_instance_free() after that.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20191107192008.32331-4-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details you
should have received a copy of the gnu general public license along
with this program if not write to the free software foundation inc
59 temple place suite 330 boston ma 02111 1307 usa
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1334 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently we allow unlimited number of timer instances, and it may
bring the system hogging way too much CPU when too many timer
instances are opened and processed concurrently. This may end up with
a soft-lockup report as triggered by syzkaller, especially when
hrtimer backend is deployed.
Since such insane number of instances aren't demanded by the normal
use case of ALSA sequencer and it merely opens a risk only for abuse,
this patch introduces the upper limit for the number of instances per
timer backend. As default, it's set to 1000, but for the fine-grained
timer like hrtimer, it's set to 100.
Reported-by: syzbot
Tested-by: Jérôme Glisse <jglisse@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Instead of the previous ugly hack, introduce a new op, disconnect, to
snd_timer_instance object for handling the wake up of pending tasks
more cleanly.
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=109431
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Orignally proposed by Sam Revitch <sam.revitch@gmail.com>.
Unregister device files at disconnection to avoid the futher accesses.
Also, the dev_unregister callback is removed and replaced with the
combination of disconnect + free.
A new function snd_card_free_when_closed() is introduced, which is
used in USB disconnect callback.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
Modules: RTC timer driver,Timer Midlevel
Add a module pointer to the timer structure and use it for refcounting
instead of the card's module pointer to prevent the global timer
modules (rtctimer and hpetimer) from being removed while in use.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
PCM Midlevel,ALSA Core,Timer Midlevel,ALSA sequencer,Virtual Midi
This patch contains the following possible cleanups:
- make needlessly global code static
- #if 0 the following unused global functions
- remove the following unneeded EXPORT_SYMBOL's
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Takashi Iwai