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Violators will be prosecuted for from ; Thu, 26 Apr 2018 06:32:14 +0100 Date: Thu, 26 Apr 2018 11:02:03 +0530 From: Vaidyanathan Srinivasan To: Shilpasri G Bhat Cc: rjw@rjwysocki.net, viresh.kumar@linaro.org, npiggin@gmail.com, benh@kernel.crashing.org, mpe@ellerman.id.au, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, ppaidipe@linux.vnet.ibm.com, stable@vger.kernel.org Subject: Re: [PATCH V3] cpufreq: powernv: Fix the hardlockup by synchronus smp_call in timer interrupt Reply-To: svaidy@linux.vnet.ibm.com References: <1524653971-4919-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: <1524653971-4919-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com> Message-Id: <20180426053203.GA13662@drishya.in.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , * Shilpa Bhat [2018-04-25 16:29:31]: > gpstate_timer_handler() uses synchronous smp_call to set the pstate > on the requested core. This causes the below hard lockup: > > [c000003fe566b320] [c0000000001d5340] smp_call_function_single+0x110/0x180 (unreliable) > [c000003fe566b390] [c0000000001d55e0] smp_call_function_any+0x180/0x250 > [c000003fe566b3f0] [c000000000acd3e8] gpstate_timer_handler+0x1e8/0x580 > [c000003fe566b4a0] [c0000000001b46b0] call_timer_fn+0x50/0x1c0 > [c000003fe566b520] [c0000000001b4958] expire_timers+0x138/0x1f0 > [c000003fe566b590] [c0000000001b4bf8] run_timer_softirq+0x1e8/0x270 > [c000003fe566b630] [c000000000d0d6c8] __do_softirq+0x158/0x3e4 > [c000003fe566b710] [c000000000114be8] irq_exit+0xe8/0x120 > [c000003fe566b730] [c000000000024d0c] timer_interrupt+0x9c/0xe0 > [c000003fe566b760] [c000000000009014] decrementer_common+0x114/0x120 > -- interrupt: 901 at doorbell_global_ipi+0x34/0x50 > LR = arch_send_call_function_ipi_mask+0x120/0x130 > [c000003fe566ba50] [c00000000004876c] > arch_send_call_function_ipi_mask+0x4c/0x130 > [c000003fe566ba90] [c0000000001d59f0] smp_call_function_many+0x340/0x450 > [c000003fe566bb00] [c000000000075f18] pmdp_invalidate+0x98/0xe0 > [c000003fe566bb30] [c0000000003a1120] change_huge_pmd+0xe0/0x270 > [c000003fe566bba0] [c000000000349278] change_protection_range+0xb88/0xe40 > [c000003fe566bcf0] [c0000000003496c0] mprotect_fixup+0x140/0x340 > [c000003fe566bdb0] [c000000000349a74] SyS_mprotect+0x1b4/0x350 > [c000003fe566be30] [c00000000000b184] 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: [4.8+] > Reported-by: Nicholas Piggin > Reported-by: Pridhiviraj Paidipeddi > Signed-off-by: Shilpasri G Bhat > --- > Changes from V2: > - Remove the check for active policy while requeing the migrated timer > Changes from V1: > - Remove smp_call in the pstate handler. > > drivers/cpufreq/powernv-cpufreq.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index 71f8682..e368e1f 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -679,6 +679,16 @@ void gpstate_timer_handler(struct timer_list *t) > > 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; > + } > > /* > * If PMCR was last updated was using fast_swtich then > @@ -718,10 +728,8 @@ void gpstate_timer_handler(struct timer_list *t) > if (gpstate_idx != gpstates->last_lpstate_idx) > queue_gpstate_timer(gpstates); > > + 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); > } Fix looks good. Acked-by: Vaidyanathan Srinivasan