linux-stable.git/kernel/time/alarmtimer.c, branch v3.18.78

alarmtimer: don't rate limit one-shot timers

2017-07-27T22:03:29+00:00

Commit ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals") sets a
minimum bound on the alarm timer interval.  This minimum bound shouldn't
be applied if the interval is 0.  Otherwise, one-shot timers will be
converted into periodic ones.

Fixes: ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals")
Reported-by: Ben Fennema 
Signed-off-by: Greg Hackmann 
Cc: stable@vger.kernel.org
Cc: John Stultz 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

alarmtimer: Rate limit periodic intervals

2017-06-26T05:10:54+00:00

commit ff86bf0c65f14346bf2440534f9ba5ac232c39a0 upstream.

The alarmtimer code has another source of potentially rearming itself too
fast. Interval timers with a very samll interval have a similar CPU hog
effect as the previously fixed overflow issue.

The reason is that alarmtimers do not implement the normal protection
against this kind of problem which the other posix timer use:

  timer expires -> queue signal -> deliver signal -> rearm timer

This scheme brings the rearming under scheduler control and prevents
permanently firing timers which hog the CPU.

Bringing this scheme to the alarm timer code is a major overhaul because it
lacks all the necessary mechanisms completely.

So for a quick fix limit the interval to one jiffie. This is not
problematic in practice as alarmtimers are usually backed by an RTC for
suspend which have 1 second resolution. It could be therefor argued that
the resolution of this clock should be set to 1 second in general, but
that's outside the scope of this fix.

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Kostya Serebryany 
Cc: syzkaller 
Cc: John Stultz 
Cc: Dmitry Vyukov 
Link: http://lkml.kernel.org/r/20170530211655.896767100@linutronix.de
Signed-off-by: Greg Kroah-Hartman

alarmtimer: Lock k_itimer during timer callback

2014-09-12T20:59:12+00:00

Locks the k_itimer's it_lock member when handling the alarm timer's
expiry callback.

The regular posix timers defined in posix-timers.c have this lock held
during timout processing because their callbacks are routed through
posix_timer_fn().  The alarm timers follow a different path, so they
ought to grab the lock somewhere else.

Cc: stable@vger.kernel.org
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Sharvil Nanavati 
Signed-off-by: Richard Larocque 
Signed-off-by: John Stultz

alarmtimer: Do not signal SIGEV_NONE timers

2014-09-12T20:59:12+00:00

Avoids sending a signal to alarm timers created with sigev_notify set to
SIGEV_NONE by checking for that special case in the timeout callback.

The regular posix timers avoid sending signals to SIGEV_NONE timers by
not scheduling any callbacks for them in the first place.  Although it
would be possible to do something similar for alarm timers, it's simpler
to handle this as a special case in the timeout.

Prior to this patch, the alarm timer would ignore the sigev_notify value
and try to deliver signals to the process anyway.  Even worse, the
sanity check for the value of sigev_signo is skipped when SIGEV_NONE was
specified, so the signal number could be bogus.  If sigev_signo was an
unitialized value (as it often would be if SIGEV_NONE is used), then
it's hard to predict which signal will be sent.

Cc: stable@vger.kernel.org
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Sharvil Nanavati 
Signed-off-by: Richard Larocque 
Signed-off-by: John Stultz

alarmtimer: Return relative times in timer_gettime

2014-09-12T20:59:11+00:00

Returns the time remaining for an alarm timer, rather than the time at
which it is scheduled to expire.  If the timer has already expired or it
is not currently scheduled, the it_value's members are set to zero.

This new behavior matches that of the other posix-timers and the POSIX
specifications.

This is a change in user-visible behavior, and may break existing
applications.  Hopefully, few users rely on the old incorrect behavior.

Cc: stable@vger.kernel.org
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Richard Cochran 
Cc: Prarit Bhargava 
Cc: Sharvil Nanavati 
Signed-off-by: Richard Larocque 
[jstultz: minor style tweak]
Signed-off-by: John Stultz

Merge tag 'staging-3.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

2014-08-05T01:36:12+00:00

Pull staging driver updates from Greg KH:
 "Here's the big pull request for the staging driver tree for 3.17-rc1.

  Lots of things in here, over 2000 patches, but the best part is this:
   1480 files changed, 39070 insertions(+), 254659 deletions(-)

  Thanks to the great work of Kristina Martšenko, 14 different staging
  drivers have been removed from the tree as they were obsolete and no
  one was willing to work on cleaning them up.  Other than the driver
  removals, loads of cleanups are in here (comedi, lustre, etc.) as well
  as the usual IIO driver updates and additions.

  All of this has been in the linux-next tree for a while"

* tag 'staging-3.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: (2199 commits)
  staging: comedi: addi_apci_1564: remove diagnostic interrupt support code
  staging: comedi: addi_apci_1564: add subdevice to check diagnostic status
  staging: wlan-ng: coding style problem fix
  staging: wlan-ng: fixing coding style problems
  staging: comedi: ii_pci20kc: request and ioremap memory
  staging: lustre: bitwise vs logical typo
  staging: dgnc: Remove unneeded dgnc_trace.c and dgnc_trace.h
  staging: dgnc: rephrase comment
  staging: comedi: ni_tio: remove some dead code
  staging: rtl8723au: Fix static symbol sparse warning
  staging: rtl8723au: usb_dvobj_init(): Remove unused variable 'pdev_desc'
  staging: rtl8723au: Do not duplicate kernel provided USB macros
  staging: rtl8723au: Remove never set struct pwrctrl_priv.bHWPowerdown
  staging: rtl8723au: Remove two never set variables
  staging: rtl8723au: RSSI_test is never set
  staging:r8190: coding style: Fixed checkpatch reported Error
  staging:r8180: coding style: Fixed too long lines
  staging:r8180: coding style: Fixed commenting style
  staging: lustre: ptlrpc: lproc_ptlrpc.c - fix dereferenceing user space buffer
  staging: lustre: ldlm: ldlm_resource.c - fix dereferenceing user space buffer
  ...

alarmtimer: Fix bug where relative alarm timers were treated as absolute

2014-07-08T08:49:36+00:00

Sharvil noticed with the posix timer_settime interface, using the
CLOCK_REALTIME_ALARM or CLOCK_BOOTTIME_ALARM clockid, if the users
tried to specify a relative time timer, it would incorrectly be
treated as absolute regardless of the state of the flags argument.

This patch corrects this, properly checking the absolute/relative flag,
as well as adds further error checking that no invalid flag bits are set.

Reported-by: Sharvil Nanavati 
Signed-off-by: John Stultz 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Prarit Bhargava 
Cc: Sharvil Nanavati 
Cc: stable  #3.0+
Link: http://lkml.kernel.org/r/1404767171-6902-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner

alarmtimer: Export symbols of alarmtimer_get_rtcdev

2014-06-20T00:30:57+00:00

Export symbol of alarmtimer_get_rtcdev so that it is used by
any driver when built as module like,
drivers/staging/android/alarm-dev.c.

CC: John Stultz 
CC: Marcus Gelderie 
Signed-off-by: Pramod Gurav 
Signed-off-by: Greg Kroah-Hartman

alarmtimer: return EINVAL instead of ENOTSUPP if rtcdev doesn't exist

2013-10-18T23:23:58+00:00

Fedora Ruby maintainer reported latest Ruby doesn't work on Fedora Rawhide
on ARM. (http://bugs.ruby-lang.org/issues/9008)

Because of, commit 1c6b39ad3f (alarmtimers: Return -ENOTSUPP if no
RTC device is present) intruduced to return ENOTSUPP when
clock_get{time,res} can't find a RTC device. However this is incorrect.

First, ENOTSUPP isn't exported to userland (ENOTSUP or EOPNOTSUP are the
closest userland equivlents).

Second, Posix and Linux man pages agree that clock_gettime and
clock_getres should return EINVAL if clk_id argument is invalid.
While the arugment that the clockid is valid, but just not supported
on this hardware could be made, this is just a technicality that
doesn't help userspace applicaitons, and only complicates error
handling.

Thus, this patch changes the code to use EINVAL.

Cc: Thomas Gleixner 
Cc: Frederic Weisbecker 
Cc: stable   #3.0 and up
Reported-by: Vit Ondruch 
Signed-off-by: KOSAKI Motohiro 
[jstultz: Tweaks to commit message to include full rational]
Signed-off-by: John Stultz

alarmtimer: Export symbols of functions declared in linux/alarmtimer.h

2013-06-12T21:02:12+00:00

Export symbols so they can be used by
drivers/staging/android/alarm-dev.c if it is built as a module.
So far alarm-dev is built-in but module support is planned (see
drivers/staging/android/TODO).

Signed-off-by: Marcus Gelderie 
[jstultz: tweaked commit message, also export newly added functions]
Signed-off-by: John Stultz