Wanpeng Li 08d0725992 tick/nohz: Fix softlockup on scheduler stalls in kvm guest ... tick_nohz_start_idle() is prevented to be called if the idle tick can't be stopped since commit 1f3b0f8243 ("tick/nohz: Optimize nohz idle enter"). As a result, after suspend/resume the host machine, full dynticks kvm guest will softlockup: NMI watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [swapper/0:0] Call Trace: default_idle+0x31/0x1a0 arch_cpu_idle+0xf/0x20 default_idle_call+0x2a/0x50 cpu_startup_entry+0x39b/0x4d0 rest_init+0x138/0x140 ? rest_init+0x5/0x140 start_kernel+0x4c1/0x4ce ? set_init_arg+0x55/0x55 ? early_idt_handler_array+0x120/0x120 x86_64_start_reservations+0x24/0x26 x86_64_start_kernel+0x142/0x14f In addition, cat /proc/stat | grep cpu in guest or host: cpu 398 16 5049 15754 5490 0 1 46 0 0 cpu0 206 5 450 0 0 0 1 14 0 0 cpu1 81 0 3937 3149 1514 0 0 9 0 0 cpu2 45 6 332 6052 2243 0 0 11 0 0 cpu3 65 2 328 6552 1732 0 0 11 0 0 The idle and iowait states are weird 0 for cpu0(housekeeping). The bug is present in both guest and host kernels, and they both have cpu0's idle and iowait states issue, however, host kernel's suspend/resume path etc will touch watchdog to avoid the softlockup. - The watchdog will not be touched in tick_nohz_stop_idle path (need be touched since the scheduler stall is expected) if idle_active flags are not detected. - The idle and iowait states will not be accounted when exit idle loop (resched or interrupt) if idle start time and idle_active flags are not set. This patch fixes it by reverting commit 1f3b0f8243 since can't stop idle tick doesn't mean can't be idle. Fixes: 1f3b0f8243 ("tick/nohz: Optimize nohz idle enter") Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> Cc: Sanjeev Yadav<sanjeev.yadav@spreadtrum.com> Cc: Gaurav Jindal<gaurav.jindal@spreadtrum.com> Cc: stable@vger.kernel.org Cc: kvm@vger.kernel.org Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Link: http://lkml.kernel.org/r/1472798303-4154-1-git-send-email-wanpeng.li@hotmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>		2016-09-02 10:25:40 +02:00
..
alarmtimer.c	alarmtimer: Fix comments describing structure fields	2016-06-20 12:47:09 -07:00
clockevents.c	clockevents: Make clockevents_subsys static	2016-07-19 10:48:06 +02:00
clocksource.c	clocksource: Make clocksource insert entry more efficient	2016-06-20 12:46:34 -07:00
hrtimer.c	hrtimer: Convert to hotplug state machine	2016-07-15 10:41:37 +02:00
itimer.c
jiffies.c
Kconfig
Makefile
ntp_internal.h
ntp.c
posix-clock.c
posix-cpu-timers.c	posix_cpu_timer: Exit early when process has been reaped	2016-07-11 17:20:12 +02:00
posix-timers.c
sched_clock.c
test_udelay.c	time: Avoid timespec in udelay_test	2016-06-20 12:47:26 -07:00
tick-broadcast-hrtimer.c	tick/broadcast-hrtimer: Set name of the ce_broadcast_hrtimer	2016-07-05 17:02:19 +02:00
tick-broadcast.c
tick-common.c
tick-internal.h	timers: Forward the wheel clock whenever possible	2016-07-07 10:35:11 +02:00
tick-oneshot.c
tick-sched.c	tick/nohz: Fix softlockup on scheduler stalls in kvm guest	2016-09-02 10:25:40 +02:00
tick-sched.h
time.c	time: remove timespec_add_safe()	2016-05-19 19:12:14 -07:00
timeconst.bc
timeconv.c	time: Add time64_to_tm()	2016-06-20 12:47:15 -07:00
timecounter.c
timekeeping_debug.c	timekeeping: Cap array access in timekeeping_debug	2016-08-24 09:34:32 +02:00
timekeeping_internal.h
timekeeping.c	timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING	2016-08-24 09:34:31 +02:00
timekeeping.h
timer_list.c
timer_stats.c	timer: Avoid using timespec	2016-06-20 12:47:33 -07:00
timer.c	timers: Fix get_next_timer_interrupt() computation	2016-08-09 09:31:55 +02:00