linux_dsm_epyc7002/arch
Anton Blanchard 8050936caf powerpc: irq work racing with timer interrupt can result in timer interrupt hang
I am seeing an issue where a CPU running perf eventually hangs.
Traces show timer interrupts happening every 4 seconds even
when a userspace task is running on the CPU. /proc/timer_list
also shows pending hrtimers have not run in over an hour,
including the scheduler.

Looking closer, decrementers_next_tb is getting set to
0xffffffffffffffff, and at that point we will never take
a timer interrupt again.

In __timer_interrupt() we set decrementers_next_tb to
0xffffffffffffffff and rely on ->event_handler to update it:

        *next_tb = ~(u64)0;
        if (evt->event_handler)
                evt->event_handler(evt);

In this case ->event_handler is hrtimer_interrupt. This will eventually
call back through the clockevents code with the next event to be
programmed:

static int decrementer_set_next_event(unsigned long evt,
                                      struct clock_event_device *dev)
{
        /* Don't adjust the decrementer if some irq work is pending */
        if (test_irq_work_pending())
                return 0;
        __get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt;

If irq work came in between these two points, we will return
before updating decrementers_next_tb and we never process a timer
interrupt again.

This looks to have been introduced by 0215f7d8c5 (powerpc: Fix races
with irq_work). Fix it by removing the early exit and relying on
code later on in the function to force an early decrementer:

       /* We may have raced with new irq work */
       if (test_irq_work_pending())
               set_dec(1);

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2014-05-12 14:29:28 +10:00
..
alpha Merge git://git.infradead.org/users/eparis/audit 2014-04-12 12:38:53 -07:00
arc ARC: Delete stale barrier.h 2014-04-18 13:49:15 -07:00
arm Shiraz has moved 2014-04-18 16:40:08 -07:00
arm64 - Documentation clarification on CPU topology and booting requirements 2014-04-08 12:06:03 -07:00
avr32 Char/Misc driver patches for 3.15-rc1 2014-04-01 16:13:21 -07:00
blackfin blackfin updates for Linux 3.15 2014-04-12 17:26:45 -07:00
c6x Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-03-31 10:59:39 -07:00
cris Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
frv PCI changes for the v3.15 merge window: 2014-04-01 15:14:04 -07:00
hexagon Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
ia64 Small workaround for a rare, but annoying, erratum 2014-04-16 11:22:45 -07:00
m32r Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
m68k Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
metag Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
microblaze Microblaze patches for 3.15-rc1 2014-04-11 11:53:45 -07:00
mips mips: export flush_icache_range 2014-04-18 16:40:09 -07:00
mn10300 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
openrisc Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
parisc Merge branch 'parisc-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2014-04-17 13:21:35 -07:00
powerpc powerpc: irq work racing with timer interrupt can result in timer interrupt hang 2014-05-12 14:29:28 +10:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-04-16 11:28:25 -07:00
score score: remove unused CPU_SCORE7 Kconfig parameter 2014-04-03 16:20:52 -07:00
sh Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
sparc Merge git://git.infradead.org/users/eparis/audit 2014-04-12 12:38:53 -07:00
tile Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
um Merge git://git.infradead.org/users/eparis/audit 2014-04-12 12:38:53 -07:00
unicore32 Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
x86 Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-04-19 10:41:43 -07:00
xtensa Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
.gitignore
Kconfig uprobes: Kconfig dependency fix 2014-03-18 16:39:33 -04:00