Commit Graph

38 Commits

Author SHA1 Message Date
Richard Larocque
474e941bed alarmtimer: Lock k_itimer during timer callback
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 <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Signed-off-by: Richard Larocque <rlarocque@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2014-09-12 13:59:12 -07:00
Richard Larocque
265b81d23a alarmtimer: Do not signal SIGEV_NONE timers
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 <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Signed-off-by: Richard Larocque <rlarocque@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2014-09-12 13:59:12 -07:00
Richard Larocque
e86fea7649 alarmtimer: Return relative times in timer_gettime
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 <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Signed-off-by: Richard Larocque <rlarocque@google.com>
[jstultz: minor style tweak]
Signed-off-by: John Stultz <john.stultz@linaro.org>
2014-09-12 13:59:11 -07:00
Linus Torvalds
53ee983378 Staging driver patches for 3.17-rc1
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.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'staging-3.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

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
  ...
2014-08-04 18:36:12 -07:00
John Stultz
16927776ae alarmtimer: Fix bug where relative alarm timers were treated as absolute
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 <sharvil@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Cc: stable <stable@vger.kernel.org> #3.0+
Link: http://lkml.kernel.org/r/1404767171-6902-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-07-08 10:49:36 +02:00
Pramod Gurav
71d5d2b722 alarmtimer: Export symbols of alarmtimer_get_rtcdev
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 <john.stultz@linaro.org>
CC: Marcus Gelderie <redmnic@gmail.com>
Signed-off-by: Pramod Gurav <pramod.gurav.etc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-06-19 17:30:57 -07:00
KOSAKI Motohiro
98d6f4dd84 alarmtimer: return EINVAL instead of ENOTSUPP if rtcdev doesn't exist
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 <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: stable <stable@vger.kernel.org>  #3.0 and up
Reported-by: Vit Ondruch <v.ondruch@tiscali.cz>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
[jstultz: Tweaks to commit message to include full rational]
Signed-off-by: John Stultz <john.stultz@linaro.org>
2013-10-18 16:23:58 -07:00
Marcus Gelderie
11682a4161 alarmtimer: Export symbols of functions declared in linux/alarmtimer.h
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 <redmnic@gmail.com>
[jstultz: tweaked commit message, also export newly added functions]
Signed-off-by: John Stultz <john.stultz@linaro.org>
2013-06-12 14:02:12 -07:00
Todd Poynor
6cffe00f7d alarmtimer: Add functions for timerfd support
Add functions needed for hooking up alarmtimer to timerfd:

* alarm_restart: Similar to hrtimer_restart, restart an alarmtimer after
  the expires time has already been updated (as with alarm_forward).

* alarm_forward_now: Similar to hrtimer_forward_now, move the expires
  time forward to an interval from the current time of the associated clock.

* alarm_start_relative: Start an alarmtimer with an expires time relative to
  the current time of the associated clock.

* alarm_expires_remaining: Similar to hrtimer_expires_remaining, return the
  amount of time remaining until alarm expiry.

Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2013-05-29 12:57:34 -07:00
John Stultz
a65bcc12ad alarmtimer: Rename alarmtimer_remove to alarmtimer_dequeue
Now that alarmtimer_remove has been simplified, change
its name to _dequeue to better match its paired _enqueue
function.

Cc: Arve Hjønnevåg <arve@android.com>
Cc: Colin Cross <ccross@android.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2012-09-24 12:38:03 -04:00
John Stultz
dae373be9f alarmtimer: Use hrtimer per-alarm instead of per-base
Arve Hjønnevåg reported numerous crashes from the
"BUG_ON(timer->state != HRTIMER_STATE_CALLBACK)" check
in __run_hrtimer after it called alarmtimer_fired.

It ends up the alarmtimer code was not properly handling
possible failures of hrtimer_try_to_cancel, and because
these faulres occur when the underlying base hrtimer is
being run, this limits the ability to properly handle
modifications to any alarmtimers on that base.

Because much of the logic duplicates the hrtimer logic,
it seems that we might as well have a per-alarmtimer
hrtimer, and avoid the extra complextity of trying to
multiplex many alarmtimers off of one hrtimer.

Thus this patch moves the hrtimer to the alarm structure
and simplifies the management logic.

Changelog:
v2:
* Includes a fix for double alarm_start calls found by
  Arve

Cc: Arve Hjønnevåg <arve@android.com>
Cc: Colin Cross <ccross@android.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Arve Hjønnevåg <arve@android.com>
Tested-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2012-09-24 12:38:02 -04:00
Todd Poynor
59a93c27c4 alarmtimer: Implement minimum alarm interval for allowing suspend
alarmtimer suspend return -EBUSY if the next alarm will fire in less
than 2 seconds.  This allows one RTC seconds tick to occur subsequent
to this check before the alarm wakeup time is set, ensuring the wakeup
time is still in the future (assuming the RTC does not tick one more
second prior to setting the alarm).

If suspend is rejected due to an imminent alarm, hold a wakeup source
for 2 seconds to process the alarm prior to reattempting suspend.

If setting the alarm incurs an -ETIME for an alarm set in the past,
or any other problem setting the alarm, abort suspend and hold a
wakelock for 1 second while the alarm is allowed to be serviced or
other hopefully transient conditions preventing the alarm clear up.

Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2012-09-24 12:38:01 -04:00
John Stultz
57c498fa5d alarmtimer: Provide accessor to alarmtimer rtc device
The Android alarm interface provides a settime call that sets both
the alarmtimer RTC device and CLOCK_REALTIME to the same value.

Since there may be multiple rtc devices, provide a hook to access the
one the alarmtimer infrastructure is using.

CC: Colin Cross <ccross@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Android Kernel Team <kernel-team@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-04-20 14:56:36 -07:00
Thomas Gleixner
c5e14e7630 alarmtimer: Don't call rtc_timer_init() when CONFIG_RTC_CLASS=n
rtc_timer_init() is not available when CONFIG_RTC_CLASS=n. Provide a
proper wrapper in the RTC section of alarmtimer.c

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
2012-03-24 12:46:23 +01:00
John Stultz
ad30dfa94c alarmtimer: Make sure we initialize the rtctimer
jonghwan Choi reported seeing warnings with the alarmtimer
code at suspend/resume time, and pointed out that the
rtctimer isn't being properly initialized.

This patch corrects this issue.

Reported-by: jonghwan Choi <jhbird.choi@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2012-03-23 16:23:12 -07:00
Thomas Gleixner
c9c024b3f3 alarmtimers: Fix time comparison
The expiry function compares the timer against current time and does
not expire the timer when the expiry time is >= now. That's wrong. If
the timer is set for now, then it must expire.

Make the condition expiry > now for breaking out the loop.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: stable@kernel.org
2011-12-06 11:38:32 +01:00
Thomas Gleixner
4523f6ada8 alarmtimers: Fix error handling
commit 8bc0daf (alarmtimers: Rework RTC device selection using class
interface) did not implement required error checks. Add them.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2011-09-14 10:54:29 +02:00
John Stultz
8bc0dafb5c alarmtimers: Rework RTC device selection using class interface
This allows cleaner detection of the RTC device being registered, rather
then probing any time someone calls alarmtimer_get_rtcdev.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:30 -07:00
John Stultz
9082c465a5 alarmtimers: Add try_to_cancel functionality
There's a number of edge cases when cancelling a alarm, so
to be sure we accurately do so, introduce try_to_cancel, which
returns proper failure errors if it cannot. Also modify cancel
to spin until the alarm is properly disabled.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:29 -07:00
John Stultz
a28cde81ab alarmtimers: Add more refined alarm state tracking
In order to allow for functionality like try_to_cancel, add
more refined  state tracking (similar to hrtimers).

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:27 -07:00
John Stultz
9e26476243 alarmtimers: Remove period from alarm structure
Now that periodic alarmtimers are managed by the handler function,
remove the period value from the alarm structure and let the handlers
manage the interval on their own.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:26 -07:00
John Stultz
d77e23acce alarmtimers: Remove interval cap limit hack
Now that the alarmtimers code has been refactored, the interval
cap limit can be removed.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:24 -07:00
John Stultz
dce75a8c71 alarmtimers: Add alarm_forward functionality
In order to avoid wasting time expiring and re-adding very high freq
periodic alarmtimers, introduce alarm_forward() which is similar to
hrtimer_forward and moves the timer to the next future expiration time
and returns the number of overruns.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:23 -07:00
John Stultz
54da23b720 alarmtimers: Push rearming peroidic timers down into alamrtimer handler
This patch pushes the periodic alarmtimer re-arming down into the alarmtimer
handler, mimicking how hrtimers handle this.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:22 -07:00
John Stultz
4b41308d2d alarmtimers: Change alarmtimer functions to return alarmtimer_restart values
In order to properly fix the denial of service issue with high freq
periodic alarm timers, we need to push the re-arming logic into the
alarm timer handler, much as the hrtimer code does.

This patch introduces alarmtimer_restart enum and changes the
alarmtimer handler declarations to use it as a return value. Further,
to ease following changes, it extends the alarmtimer handler functions
to also take the time at expiration. No logic is yet modified.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 14:55:20 -07:00
John Stultz
6af7e471e5 alarmtimers: Avoid possible denial of service with high freq periodic timers
Its possible to jam up the alarm timers by setting very small interval
timers, which will cause the alarmtimer subsystem to spend all of its time
firing and restarting timers. This can effectivly lock up a box.

A deeper fix is needed, closely mimicking the hrtimer code, but for now
just cap the interval to 100us to avoid userland hanging the system.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: stable@kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 10:26:09 -07:00
John Stultz
ea7802f630 alarmtimers: Memset itimerspec passed into alarm_timer_get
Following common_timer_get, zero out the itimerspec passed in.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: stable@kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 07:10:09 -07:00
John Stultz
971c90bfa2 alarmtimers: Avoid possible null pointer traversal
We don't check if old_setting is non null before assigning it, so
correct this.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: stable@kernel.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-08-10 07:09:53 -07:00
John Stultz
1c6b39ad3f alarmtimers: Return -ENOTSUPP if no RTC device is present
Toralf Förster and Richard Weinberger noted that if there is
no RTC device, the alarm timers core prints out an annoying
"ALARM timers will not wake from suspend" message.

This warning has been removed in a previous patch, however
the issue still remains:  The original idea was to support
alarm timers even if there was no rtc device, as long as the
system didn't go into suspend.

However, after further consideration, communicating to the application
that alarmtimers are not fully functional seems like the better
solution.

So this patch makes it so we return -ENOTSUPP to any posix _ALARM
clockid calls if there is no backing RTC device on the system.

Further this changes the behavior where when there is no rtc device
we will check for one on clock_getres, clock_gettime, timer_create,
and timer_nsleep instead of on suspend.

CC: Toralf Förster <toralf.foerster@gmx.de>
CC: Richard Weinberger <richard@nod.at
CC: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Reported by: Richard Weinberger <richard@nod.at>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-06-21 16:32:28 -07:00
John Stultz
c008ba58af alarmtimers: Handle late rtc module loading
The alarmtimers code currently picks a rtc device to use at
late init time. However, if your rtc driver is loaded as a module,
it may be registered after the alarmtimers late init code, leaving
the alarmtimers nonfunctional.

This patch moves the the rtcdevice selection to when we actually try
to use it, allowing us to make use of rtc modules that may have been
loaded at any point since bootup.

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Meelis Roos <mroos@ut.ee>
Reported-by: Meelis Roos <mroos@ut.ee>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-06-21 15:38:33 -07:00
Thomas Gleixner
ab8177bc53 hrtimers: Avoid touching inactive timer bases
Instead of iterating over all possible timer bases avoid it by marking
the active bases in the cpu base.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2011-05-23 13:59:54 +02:00
Thomas Gleixner
179eb03268 alarmtimer: Drop device refcount after rtc_open()
class_find_device() takes a refcount on the rtc device. rtc_open()
takes another one, so we can drop it after the rtc_open() call.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
2011-05-04 08:18:34 +02:00
Thomas Gleixner
ce788f930b alarmtimer: Check return value of class_find_device()
alarmtimer_late_init() uses class_find_device() to find a alarm
capable rtc device. The match callback stores a pointer to the name in
the char pointer handed in from the call site. alarmtimer_late_init()
checks the char pointer for NULL, but the pointer is on the stack and
not initialized to NULL before the call. So it can have random content
when the match function did not identify a device, which leads to
random access in the following rtc_open() call where the pointer is
dereferenced

Instead of relying on the char pointer, check the return value of
class_find_device. If a device is found then the name pointer is valid
as well.

Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2011-05-04 08:18:17 +02:00
John Stultz
472647dcd7 timers: Fix alarmtimer build issues when CONFIG_RTC_CLASS=n
Ingo pointed out that the alarmtimers won't build if CONFIG_RTC_CLASS=n.
This patch adds proper ifdefs to the alarmtimer code to disable the rtc
usage if it is not built in.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2011-05-02 21:36:57 +02:00
John Stultz
7068b7a162 timers: Remove delayed irqwork from alarmtimers implementation
Thomas asked about the delayed irq work in the alarmtimers code,
and I realized that it was a legacy from when the alarmtimer base
lock was a mutex (due to concerns that we'd be interacting with
the RTC device, which is protected by mutexes).

Since the alarmtimer base is now protected by a spinlock, we can
simply execute alarmtimer functions directly from the hrtimer
callback. Should any future alarmtimer functions sleep, they can
simply manage scheduling any delayed work themselves.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-04-28 13:39:18 -07:00
John Stultz
180bf812ce timers: Improve alarmtimer comments and minor fixes
This patch addresses a number of minor comment improvements and
other minor issues from Thomas' review of the alarmtimers code.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-04-28 13:39:17 -07:00
John Stultz
9a7adcf5c6 timers: Posix interface for alarm-timers
This patch exposes alarm-timers to userland via the posix clock
and timers interface, using two new clockids: CLOCK_REALTIME_ALARM
and CLOCK_BOOTTIME_ALARM. Both clockids behave identically to
CLOCK_REALTIME and CLOCK_BOOTTIME, respectively, but timers
set against the _ALARM suffixed clockids will wake the system if
it is suspended.

Some background can be found here:
	https://lwn.net/Articles/429925/

The concept for Alarm-timers was inspired by the Android Alarm
driver (by Arve Hjønnevåg) found in the Android kernel tree.

See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36

While the in-kernel interface is pretty similar between
alarm-timers and Android alarm driver, the user-space interface
for the Android alarm driver is via ioctls to a new char device.
As mentioned above, I've instead chosen to export this functionality
via the posix interface, as it seemed a little simpler and avoids
creating duplicate interfaces to things like CLOCK_REALTIME and
CLOCK_MONOTONIC under alternate names (ie:ANDROID_ALARM_RTC and
ANDROID_ALARM_SYSTEMTIME).

The semantics of the Android alarm driver are different from what
this posix interface provides. For instance, threads other then
the thread waiting on the Android alarm driver are able to modify
the alarm being waited on. Also this interface does not allow
the same wakelock semantics that the Android driver provides
(ie: kernel takes a wakelock on RTC alarm-interupt, and holds it
through process wakeup, and while the process runs, until the
process either closes the char device or calls back in to wait
on a new alarm).

One potential way to implement similar semantics may be via
the timerfd infrastructure, but this needs more research.

There may also need to be some sort of sysfs system level policy
hooks that allow alarm timers to be disabled to keep them
from firing at inappropriate times (ie: laptop in a well insulated
bag, mid-flight).

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-04-26 14:01:46 -07:00
John Stultz
ff3ead96d1 timers: Introduce in-kernel alarm-timer interface
This provides the in kernel interface and infrastructure for
alarm-timers.

Alarm-timers are a hybrid style timer, similar to hrtimers,
but when the system is suspended, the RTC device is set to
fire and wake the system for when the soonest alarm-timer
expires.

The concept for Alarm-timers was inspired by the Android Alarm
driver (by Arve Hjønnevåg) found in the Android kernel tree.

See: http://android.git.kernel.org/?p=kernel/common.git;a=blob;f=drivers/rtc/alarm.c;h=1250edfbdf3302f5e4ea6194847c6ef4bb7beb1c;hb=android-2.6.36

This in-kernel interface should be fairly compatible with the
Android alarm driver in-kernel interface, but has the advantage
of utilizing the new RTC timerqueue code instead of doing direct
RTC manipulation.

CC: Arve Hjønnevåg <arve@android.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-04-26 14:01:44 -07:00