4.9-stable review patch. If anyone has any objections, please let me know.
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From: Shilpasri G Bhat shilpa.bhat@linux.vnet.ibm.com
commit c0f7f5b6c69107ca92909512533e70258ee19188 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/cpufreq/powernv-cpufreq.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
--- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -599,6 +599,16 @@ void gpstate_timer_handler(unsigned long
if (!spin_trylock(&gpstates->gpstate_lock)) return; + /* + * If the timer has migrated to the different cpu then bring + * it back to one of the policy->cpus + */ + if (!cpumask_test_cpu(raw_smp_processor_id(), policy->cpus)) { + gpstates->timer.expires = jiffies + msecs_to_jiffies(1); + add_timer_on(&gpstates->timer, cpumask_first(policy->cpus)); + spin_unlock(&gpstates->gpstate_lock); + return; + }
gpstates->last_sampled_time += time_diff; gpstates->elapsed_time += time_diff; @@ -626,10 +636,8 @@ void gpstate_timer_handler(unsigned long gpstates->last_gpstate_idx = pstate_to_idx(freq_data.gpstate_id); gpstates->last_lpstate_idx = pstate_to_idx(freq_data.pstate_id);
+ set_pstate(&freq_data); spin_unlock(&gpstates->gpstate_lock); - - /* Timer may get migrated to a different cpu on cpu hot unplug */ - smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1); }
/*