linux.git/kernel/time, branch v4.16.13

tick/broadcast: Use for_each_cpu() specially on UP kernels

2018-05-22T16:56:24+00:00

commit 5596fe34495cf0f645f417eb928ef224df3e3cb4 upstream.

for_each_cpu() unintuitively reports CPU0 as set independent of the actual
cpumask content on UP kernels. This causes an unexpected PIT interrupt
storm on a UP kernel running in an SMP virtual machine on Hyper-V, and as
a result, the virtual machine can suffer from a strange random delay of 1~20
minutes during boot-up, and sometimes it can hang forever.

Protect if by checking whether the cpumask is empty before entering the
for_each_cpu() loop.

[ tglx: Use !IS_ENABLED(CONFIG_SMP) instead of #ifdeffery ]

Signed-off-by: Dexuan Cui 
Signed-off-by: Thomas Gleixner 
Cc: Josh Poulson 
Cc: "Michael Kelley (EOSG)" 
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
Cc: stable@vger.kernel.org
Cc: Rakib Mullick 
Cc: Jork Loeser 
Cc: Greg Kroah-Hartman 
Cc: Andrew Morton 
Cc: KY Srinivasan 
Cc: Linus Torvalds 
Cc: Alexey Dobriyan 
Cc: Dmitry Vyukov 
Link: https://lkml.kernel.org/r/KL1P15301MB000678289FE55BA365B3279ABF990@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM
Link: https://lkml.kernel.org/r/KL1P15301MB0006FA63BC22BEB64902EAA0BF930@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM
Signed-off-by: Greg Kroah-Hartman

clocksource: Consistent de-rate when marking unstable

2018-05-09T07:53:13+00:00

commit cd2af07d823e5287cd6c91d54337348c2a873462 upstream.

When a registered clocksource gets marked unstable the watchdog_kthread
will de-rate and re-select the clocksource. Ensure it also de-rates
when getting called on an unregistered clocksource.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Rafael J. Wysocki 
Cc: len.brown@intel.com
Cc: rjw@rjwysocki.net
Cc: diego.viola@gmail.com
Cc: rui.zhang@intel.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180430100344.594904898@infradead.org
Signed-off-by: Greg Kroah-Hartman

clocksource: Initialize cs->wd_list

2018-05-09T07:53:13+00:00

commit 5b9e886a4af97574ca3ce1147f35545da0e7afc7 upstream.

A number of places relies on list_empty(&cs->wd_list), however the
list_head does not get initialized. Do so upon registration, such that
thereafter it is possible to rely on list_empty() correctly reflecting
the list membership status.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Thomas Gleixner 
Tested-by: Diego Viola 
Reviewed-by: Rafael J. Wysocki 
Cc: stable@vger.kernel.org
Cc: len.brown@intel.com
Cc: rjw@rjwysocki.net
Cc: rui.zhang@intel.com
Link: https://lkml.kernel.org/r/20180430100344.472662715@infradead.org
Signed-off-by: Greg Kroah-Hartman

clocksource: Allow clocksource_mark_unstable() on unregistered clocksources

2018-05-09T07:53:13+00:00

commit 2aae7bcfa4104b770e6f612356adb8d66c6144d6 upstream.

Because of how the code flips between tsc-early and tsc clocksources
it might need to mark one or both unstable. The current code in
mark_tsc_unstable() only worked because previously it registered the
tsc clocksource once and then never touched it.

Since it now unregisters the tsc-early clocksource, it needs to know
if a clocksource got unregistered and the current cs->mult test
doesn't work for that. Instead use list_empty(&cs->list) to test for
registration.

Furthermore, since clocksource_mark_unstable() needs to place the cs
on the wd_list, it links the cs->list and cs->wd_list serialization.
It must not see a clocsource registered (!empty cs->list) but already
past dequeue_watchdog(). So place {en,de}queue{,_watchdog}() under the
same lock.

Provided cs->list is initialized to empty, this then allows us to
unconditionally use clocksource_mark_unstable(), regardless of the
registration state.

Fixes: aa83c45762a2 ("x86/tsc: Introduce early tsc clocksource")
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Rafael J. Wysocki 
Tested-by: Diego Viola 
Cc: len.brown@intel.com
Cc: rjw@rjwysocki.net
Cc: diego.viola@gmail.com
Cc: rui.zhang@intel.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180502135312.GS12217@hirez.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman

tick/sched: Do not mess with an enqueued hrtimer

2018-05-01T19:47:30+00:00

commit 1f71addd34f4c442bec7d7c749acc1beb58126f2 upstream.

Kaike reported that in tests rdma hrtimers occasionaly stopped working. He
did great debugging, which provided enough context to decode the problem.

CPU 3			     	      	     CPU 2

idle
start sched_timer expires = 712171000000
 queue->next = sched_timer
					    start rdmavt timer. expires = 712172915662
					    lock(baseof(CPU3))
tick_nohz_stop_tick()
tick = 716767000000			    timerqueue_add(tmr)

hrtimer_set_expires(sched_timer, tick);
  sched_timer->expires = 716767000000  <---- FAIL
					     if (tmr->expires < queue->next->expires)
hrtimer_start(sched_timer)		          queue->next = tmr;
lock(baseof(CPU3))
					     unlock(baseof(CPU3))
timerqueue_remove()
timerqueue_add()

ts->sched_timer is queued and queue->next is pointing to it, but then
ts->sched_timer.expires is modified.

This not only corrupts the ordering of the timerqueue RB tree, it also
makes CPU2 see the new expiry time of timerqueue->next->expires when
checking whether timerqueue->next needs to be updated. So CPU2 sees that
the rdma timer is earlier than timerqueue->next and sets the rdma timer as
new next.

Depending on whether it had also seen the new time at RB tree enqueue, it
might have queued the rdma timer at the wrong place and then after removing
the sched_timer the RB tree is completely hosed.

The problem was introduced with a commit which tried to solve inconsistency
between the hrtimer in the tick_sched data and the underlying hardware
clockevent. It split out hrtimer_set_expires() to store the new tick time
in both the NOHZ and the NOHZ + HIGHRES case, but missed the fact that in
the NOHZ + HIGHRES case the hrtimer might still be queued.

Use hrtimer_start(timer, tick...) for the NOHZ + HIGHRES case which sets
timer->expires after canceling the timer and move the hrtimer_set_expires()
invocation into the NOHZ only code path which is not affected as it merily
uses the hrtimer as next event storage so code pathes can be shared with
the NOHZ + HIGHRES case.

Fixes: d4af6d933ccf ("nohz: Fix spurious warning when hrtimer and clockevent get out of sync")
Reported-by: "Wan Kaike" 
Signed-off-by: Thomas Gleixner 
Acked-by: Frederic Weisbecker 
Cc: "Marciniszyn Mike" 
Cc: Anna-Maria Gleixner 
Cc: linux-rdma@vger.kernel.org
Cc: "Dalessandro Dennis" 
Cc: "Fleck John" 
Cc: stable@vger.kernel.org
Cc: Peter Zijlstra 
Cc: Frederic Weisbecker 
Cc: "Weiny Ira" 
Cc: "linux-rdma@vger.kernel.org"
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1804241637390.1679@nanos.tec.linutronix.de
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1804242119210.1597@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman

alarmtimer: Init nanosleep alarm timer on stack

2018-04-26T09:00:37+00:00

commit bd03143007eb9b03a7f2316c677780561b68ba2a upstream.

syszbot reported the following debugobjects splat:

 ODEBUG: object is on stack, but not annotated
 WARNING: CPU: 0 PID: 4185 at lib/debugobjects.c:328

 RIP: 0010:debug_object_is_on_stack lib/debugobjects.c:327 [inline]
 debug_object_init+0x17/0x20 lib/debugobjects.c:391
 debug_hrtimer_init kernel/time/hrtimer.c:410 [inline]
 debug_init kernel/time/hrtimer.c:458 [inline]
 hrtimer_init+0x8c/0x410 kernel/time/hrtimer.c:1259
 alarm_init kernel/time/alarmtimer.c:339 [inline]
 alarm_timer_nsleep+0x164/0x4d0 kernel/time/alarmtimer.c:787
 SYSC_clock_nanosleep kernel/time/posix-timers.c:1226 [inline]
 SyS_clock_nanosleep+0x235/0x330 kernel/time/posix-timers.c:1204
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

This happens because the hrtimer for the alarm nanosleep is on stack, but
the code does not use the proper debug objects initialization.

Split out the code for the allocated use cases and invoke
hrtimer_init_on_stack() for the nanosleep related functions.

Reported-by: syzbot+a3e0726462b2e346a31d@syzkaller.appspotmail.com
Signed-off-by: Thomas Gleixner 
Cc: John Stultz 
Cc: syzkaller-bugs@googlegroups.com
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1803261528270.1585@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman

posix-cpu-timers: Ensure set_process_cpu_timer is always evaluated

2018-04-26T09:00:36+00:00

commit c3bca5d450b620dd3d36e14b5e1f43639fd47d6b upstream.

Commit a9445e47d897 ("posix-cpu-timers: Make set_process_cpu_timer()
more robust") moved the check into the 'if' statement. Unfortunately,
it did so on the right side of an && which means that it may get short
circuited and never evaluated. This is easily reproduced with:

$ cat loop.c
void main() {
  struct rlimit res;
  /* set the CPU time limit */
  getrlimit(RLIMIT_CPU,&res);
  res.rlim_cur = 2;
  res.rlim_max = 2;
  setrlimit(RLIMIT_CPU,&res);

  while (1);
}

Which will hang forever instead of being killed. Fix this by pulling the
evaluation out of the if statement but checking the return value instead.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1568337
Fixes: a9445e47d897 ("posix-cpu-timers: Make set_process_cpu_timer() more robust")
Signed-off-by: Laura Abbott 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Cc: "Max R . P . Grossmann" 
Cc: John Stultz 
Link: https://lkml.kernel.org/r/20180417215742.2521-1-labbott@redhat.com
Signed-off-by: Greg Kroah-Hartman

posix-timers: Protect posix clock array access against speculation

2018-03-22T11:29:27+00:00

The clockid argument of clockid_to_kclock() comes straight from user space
via various syscalls and is used as index into the posix_clocks array.

Protect it against spectre v1 array out of bounds speculation. Remove the
redundant check for !posix_clock[id] as this is another source for
speculation and does not provide any advantage over the return
posix_clock[id] path which returns NULL in that case anyway.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Acked-by: Dan Williams 
Cc: Rasmus Villemoes 
Cc: Greg KH 
Cc: stable@vger.kernel.org
Cc: Linus Torvalds 
Cc: David Woodhouse 
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1802151718320.1296@nanos.tec.linutronix.de

timers: Forward timer base before migrating timers

2018-02-28T22:34:33+00:00

On CPU hotunplug the enqueued timers of the unplugged CPU are migrated to a
live CPU. This happens from the control thread which initiated the unplug.

If the CPU on which the control thread runs came out from a longer idle
period then the base clock of that CPU might be stale because the control
thread runs prior to any event which forwards the clock.

In such a case the timers from the unplugged CPU are queued on the live CPU
based on the stale clock which can cause large delays due to increased
granularity of the outer timer wheels which are far away from base:;clock.

But there is a worse problem than that. The following sequence of events
illustrates it:

 - CPU0 timer1 is queued expires = 59969 and base->clk = 59131.

   The timer is queued at wheel level 2, with resulting expiry time = 60032
   (due to level granularity).

 - CPU1 enters idle @60007, with next timer expiry @60020.

 - CPU0 is hotplugged at @60009

 - CPU1 exits idle and runs the control thread which migrates the
   timers from CPU0

   timer1 is now queued in level 0 for immediate handling in the next
   softirq because the requested expiry time 59969 is before CPU1 base->clk
   60007

 - CPU1 runs code which forwards the base clock which succeeds because the
   next expiring timer. which was collected at idle entry time is still set
   to 60020.

   So it forwards beyond 60007 and therefore misses to expire the migrated
   timer1. That timer gets expired when the wheel wraps around again, which
   takes between 63 and 630ms depending on the HZ setting.

Address both problems by invoking forward_timer_base() for the control CPUs
timer base. All other places, which might run into a similar problem
(mod_timer()/add_timer_on()) already invoke forward_timer_base() to avoid
that.

[ tglx: Massaged comment and changelog ]

Fixes: a683f390b93f ("timers: Forward the wheel clock whenever possible")
Co-developed-by: Neeraj Upadhyay 
Signed-off-by: Neeraj Upadhyay 
Signed-off-by: Lingutla Chandrasekhar 
Signed-off-by: Thomas Gleixner 
Cc: Anna-Maria Gleixner 
Cc: linux-arm-msm@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180118115022.6368-1-clingutla@codeaurora.org

vfs: do bulk POLL* -> EPOLL* replacement

2018-02-11T22:34:03+00:00

This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:

    for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
        L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
        for f in $L; do sed -i "-es/^\([^\"]*\)\(\\)/\\1E\\2/" $f; done
    done

with de-mangling cleanups yet to come.

NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do.  But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.

The next patch from Al will sort out the final differences, and we
should be all done.

Scripted-by: Al Viro 
Signed-off-by: Linus Torvalds