| Message ID | 1524646968-526-1-git-send-email-shilpa.bhat@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On 25-04-18, 14:32, Shilpasri G Bhat wrote: > 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: <stable@vger.kernel.org> [4.8+] > 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> > --- > Changes from V1: > - Remove smp_call in the pstate handler. > > drivers/cpufreq/powernv-cpufreq.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index 71f8682..dc8ffb5 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -679,6 +679,25 @@ 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)) { > + /* > + * Timer should be deleted if policy is inactive. > + * If policy is active then re-queue on one of the > + * policy->cpus. > + */ This looks racy. Shouldn't you guarantee that the timer is already removed in a synchronous way before de-activating the policy ? > + if (!cpumask_empty(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 +737,8 @@ 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); > } > > /* > -- > 1.8.3.1
Hi, On 04/25/2018 02:47 PM, Viresh Kumar wrote: > On 25-04-18, 14:32, Shilpasri G Bhat wrote: >> 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: <stable@vger.kernel.org> [4.8+] >> 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> >> --- >> Changes from V1: >> - Remove smp_call in the pstate handler. >> >> drivers/cpufreq/powernv-cpufreq.c | 23 ++++++++++++++++++++--- >> 1 file changed, 20 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c >> index 71f8682..dc8ffb5 100644 >> --- a/drivers/cpufreq/powernv-cpufreq.c >> +++ b/drivers/cpufreq/powernv-cpufreq.c >> @@ -679,6 +679,25 @@ 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)) { >> + /* >> + * Timer should be deleted if policy is inactive. >> + * If policy is active then re-queue on one of the >> + * policy->cpus. >> + */ > > This looks racy. Shouldn't you guarantee that the timer is already > removed in a synchronous way before de-activating the policy ? > The timer is deleted in driver->stop_cpu(). So we ensure to remove the timer before de-activating the policy. >> + if (!cpumask_empty(policy->cpus)) { So are you suggesting to remove ^^ the check for active policy here? (I put that as a safety check.) Thanks and Regards, Shilpa >> + 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 +737,8 @@ 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); >> } >> >> /* >> -- >> 1.8.3.1 >
On 25-04-18, 15:32, Shilpasri G Bhat wrote: > Hi, > > On 04/25/2018 02:47 PM, Viresh Kumar wrote: > > On 25-04-18, 14:32, Shilpasri G Bhat wrote: > >> 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: <stable@vger.kernel.org> [4.8+] > >> 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> > >> --- > >> Changes from V1: > >> - Remove smp_call in the pstate handler. > >> > >> drivers/cpufreq/powernv-cpufreq.c | 23 ++++++++++++++++++++--- > >> 1 file changed, 20 insertions(+), 3 deletions(-) > >> > >> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > >> index 71f8682..dc8ffb5 100644 > >> --- a/drivers/cpufreq/powernv-cpufreq.c > >> +++ b/drivers/cpufreq/powernv-cpufreq.c > >> @@ -679,6 +679,25 @@ 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)) { > >> + /* > >> + * Timer should be deleted if policy is inactive. > >> + * If policy is active then re-queue on one of the > >> + * policy->cpus. > >> + */ > > > > This looks racy. Shouldn't you guarantee that the timer is already > > removed in a synchronous way before de-activating the policy ? > > > > The timer is deleted in driver->stop_cpu(). So we ensure to remove the timer > before de-activating the policy. > > > >> + if (!cpumask_empty(policy->cpus)) { > > So are you suggesting to remove ^^ the check for active policy here? > (I put that as a safety check.) Either you are sure or you are not, and you don't need a safety check if you are sure :)
diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index 71f8682..dc8ffb5 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -679,6 +679,25 @@ 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)) { + /* + * Timer should be deleted if policy is inactive. + * If policy is active then re-queue on one of the + * policy->cpus. + */ + if (!cpumask_empty(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 +737,8 @@ 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); } /*
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: <stable@vger.kernel.org> [4.8+] 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> --- Changes from V1: - Remove smp_call in the pstate handler. drivers/cpufreq/powernv-cpufreq.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)