Turn restart_block.nanosleep.{rmtp,compat_rmtp} into a tagged union (kind =
1 -> native, kind = 2 -> compat, kind = 0 -> nothing) and make the places
doing actual copyout handle compat as well as native (that will become a
helper in the next commit). Result: compat wrappers, messing with
reassignments, etc. are gone.
[ tglx: Folded in a variant of Peter Zijlstras enum patch ]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-6-viro@ZenIV.linux.org.uk
The hrtimer nanosleep() implementation can be simplified by moving the copy
out of the remaining time to do_nanosleep() which is shared between the
real nanosleep function and the restart function.
The pointer to the timespec64 which is updated is already stored in the
restart block at the call site, so the seperate handling of nanosleep and
restart function can be avoided.
[ tglx: Added changelog ]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-4-viro@ZenIV.linux.org.uk
The alarmtimer nanosleep() implementation can be simplified by moving the
copy out of the remaining time to alarmtimer_do_nsleep() which is shared
between the real nanosleep function and the restart function.
The pointer to the timespec64 which is updated has to be stored in the
restart block anyway. Instead of storing it only in the restart case, store
it before calling alarmtimer_do_nsleep() and copy the remaining time in the
signal exit path.
[ tglx: Added changelog ]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-2-viro@ZenIV.linux.org.uk
The posix-cpu-timer nanosleep() implementation can be simplified by moving
the copy out of the remaining time to do_cpu_nanosleep() which is shared
between the real nanosleep function and the restart function.
The pointer to the timespec64 which is updated has to be stored in the
restart block anyway. Instead of storing it only in the restart case, store
it before calling do_cpu_nanosleep() and copy the remaining time in the
signal exit path.
[ tglx: Added changelog ]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-1-viro@ZenIV.linux.org.uk
The sanity check ensuring that the tick expiry cache (ts->next_tick)
is actually in sync with the hardware clock (dev->next_event) makes the
wrong assumption that the clock can't be programmed later than the
hrtimer deadline.
In fact the clock hardware can be programmed later on some conditions
such as:
* The hrtimer deadline is already in the past.
* The hrtimer deadline is earlier than the minimum delay supported
by the hardware.
Such conditions can be met when we program the tick, for example if the
last jiffies update hasn't been seen by the current CPU yet, we may
program the hrtimer to a deadline that is earlier than ktime_get()
because last_jiffies_update is our timestamp base to compute the next
tick.
As a result, we can randomly observe such warning:
WARNING: CPU: 5 PID: 0 at kernel/time/tick-sched.c:794 tick_nohz_stop_sched_tick kernel/time/tick-sched.c:791 [inline]
Call Trace:
tick_nohz_irq_exit
tick_irq_exit
irq_exit
exiting_irq
smp_call_function_interrupt
smp_call_function_single_interrupt
call_function_single_interrupt
Therefore, let's rather make sure that the tick expiry cache is sync'ed
with the tick hrtimer deadline, against which it is not supposed to
drift away. The clock hardware instead has its own will and can't be
used as a reliable comparison point.
Reported-and-tested-by: Sasha Levin <alexander.levin@verizon.com>
Reported-and-tested-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: James Hartsock <hartsjc@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Wright <tim@binbash.co.uk>
Link: http://lkml.kernel.org/r/1497326654-14122-1-git-send-email-fweisbec@gmail.com
[ Minor readability edit. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The recent rework of the posix timer internals broke the magic posix
mechanism, which requires that relative timers are not affected by
modifications of the underlying clock. That means relative CLOCK_REALTIME
timers cannot use CLOCK_REALTIME, because that can be set and adjusted. The
underlying hrtimer switches the clock for these timers to CLOCK_MONOTONIC.
That still works, but reading the remaining time of such a timer has been
broken in the rework. The old code used the hrtimer internals directly and
avoided the posix clock callbacks. Now common_timer_get() uses the
underlying kclock->timer_get() callback, which is still CLOCK_REALTIME
based. So the remaining time of such a timer is calculated against the
wrong time base.
Handle it by switching the k_itimer->kclock pointer according to the
resulting hrtimer mode. k_itimer->it_clock still contains CLOCK_REALTIME
because the timer might be set with ABSTIME later and then it needs to
switch back to the realtime posix clock implementation.
Fixes: eae1c4ae27 ("posix-timers: Make use of cancel/arm callbacks")
Reported-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Link: http://lkml.kernel.org/r/20170609201156.GB21491@outlook.office365.com
The refactoring of the posix-timer core to allow better code sharing
introduced inverted logic vs. SIGEV_NONE timers in common_timer_get().
That causes hrtimer_forward() to be called on active timers, which
rightfully triggers the warning hrtimer_forward().
Make sig_none what it says: signal mode == SIGEV_NONE.
Fixes: 91d57bae08 ("posix-timers: Make use of forward/remaining callbacks")
Reported-by: Ye Xiaolong <xiaolong.ye@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170609104457.GA39907@inn.lkp.intel.com
The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013
by commit 0edd1b1784 ("nohz_full: Add full-system-idle state machine"),
but has not been used. This commit therefore removes it.
If it turns out to be needed later, this commit can always be reverted.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
When the tick is stopped and we reach the dynticks evaluation code on
IRQ exit, we perform a soft tick restart if we observe an expired timer
from there. It means we program the nearest possible tick but we stay in
dynticks mode (ts->tick_stopped = 1) because we may need to stop the tick
again after that expired timer is handled.
Now this solution works most of the time but if we suffer an IRQ storm
and those interrupts trigger faster than the hardware clockevents min
delay, our tick won't fire until that IRQ storm is finished.
Here is the problem: on IRQ exit we reprog the timer to at least
NOW() + min_clockevents_delay. Another IRQ fires before the tick so we
reschedule again to NOW() + min_clockevents_delay, etc... The tick
is eternally rescheduled min_clockevents_delay ahead.
A solution is to simply remove this soft tick restart. After all
the normal dynticks evaluation path can handle 0 delay just fine. And
by doing that we benefit from the optimization branch which avoids
clock reprogramming if the clockevents deadline hasn't changed since
the last reprog. This fixes our issue because we don't do repetitive
clock reprog that always add hardware min delay.
As a side effect it should even optimize the 0 delay path in general.
Reported-and-tested-by: Octavian Purdila <octavian.purdila@nxp.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1496328429-13317-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The only user of this facility is ptp_clock, which does not implement any of
those functions.
Remove them to prevent accidental users. Especially the interval timer
interfaces are now more or less impossible to implement because the
necessary infrastructure has been confined to the core code. Aside of that
it's really complex to make these callbacks implemented according to spec
as the alarm timer implementation demonstrates. If at all then a nanosleep
callback might be a reasonable extension. For now keep just what ptp_clock
needs.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20170530211656.145036286@linutronix.de
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 <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kostya Serebryany <kcc@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170530211655.896767100@linutronix.de
Andrey reported a alartimer related RCU stall while fuzzing the kernel with
syzkaller.
The reason for this is an overflow in ktime_add() which brings the
resulting time into negative space and causes immediate expiry of the
timer. The following rearm with a small interval does not bring the timer
back into positive space due to the same issue.
This results in a permanent firing alarmtimer which hogs the CPU.
Use ktime_add_safe() instead which detects the overflow and clamps the
result to KTIME_SEC_MAX.
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kostya Serebryany <kcc@google.com>
Cc: syzkaller <syzkaller@googlegroups.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170530211655.802921648@linutronix.de
Some freezer related variables are only used when either CONFIG_POSIX_TIMER
or CONFIG_RTC_CLASS are enabled. Hide them when both are off.
Fixes: d3ba5a9a34 ("posix-timers: Make posix_clocks immutable")
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Christoph Helwig <hch@lst.de>
