Commits
Shilpasri G Bhat committed c0f7f5b6c69
cpufreq: powernv: Fix hardlockup due to synchronous smp_call in timer interrupt
gpstate_timer_handler() uses synchronous smp_call to set the pstate
on the requested core. This causes the below hard lockup:
smp_call_function_single+0x110/0x180 (unreliable)
smp_call_function_any+0x180/0x250
gpstate_timer_handler+0x1e8/0x580
call_timer_fn+0x50/0x1c0
expire_timers+0x138/0x1f0
run_timer_softirq+0x1e8/0x270
__do_softirq+0x158/0x3e4
irq_exit+0xe8/0x120
timer_interrupt+0x9c/0xe0
decrementer_common+0x114/0x120
-- interrupt: 901 at doorbell_global_ipi+0x34/0x50
LR = arch_send_call_function_ipi_mask+0x120/0x130
arch_send_call_function_ipi_mask+0x4c/0x130
smp_call_function_many+0x340/0x450
pmdp_invalidate+0x98/0xe0
change_huge_pmd+0xe0/0x270
change_protection_range+0xb88/0xe40
mprotect_fixup+0x140/0x340
SyS_mprotect+0x1b4/0x350
system_call+0x58/0x6c
One way to avoid this is removing the smp-call. We can ensure that the
timer always runs on one of the policy-cpus. If the timer gets
migrated to a cpu outside the policy then re-queue it back on the
policy->cpus. This way we can get rid of the smp-call which was being
used to set the pstate on the policy->cpus.
Fixes: 7bc54b652f13 ("timers, cpufreq/powernv: Initialize the gpstate timer as pinned")
Cc: stable@vger.kernel.org # v4.8+
Reported-by: Nicholas Piggin <npiggin@gmail.com>
Reported-by: Pridhiviraj Paidipeddi <ppaidipe@linux.vnet.ibm.com>
Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>