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Date: Tue, 3 May 2016 18:48:51 +0530 From: Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com> To: Viresh Kumar <viresh.kumar@...aro.org> Cc: rjw@...ysocki.net, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org Subject: Re: [PATCH -next 1/2] cpufreq: powernv: Move smp_call_function_any() out of irq safe block Hi Viresh, On 05/03/2016 05:19 PM, Viresh Kumar wrote: > On 03-05-16, 15:10, Akshay Adiga wrote: >> Fixing a WARN_ON caused by smp_call_function_any() when irq is disabled, >> because of changes made in the patch >> ('cpufreq: powernv: Ramp-down global pstate slower than local-pstate') >> https://patchwork.ozlabs.org/patch/612058/ >> >> WARNING: CPU: 0 PID: 4 at kernel/smp.c:291 >> smp_call_function_single+0x170/0x180 >> >> Call Trace: >> [c0000007f648f9f0] [c0000007f648fa90] 0xc0000007f648fa90 (unreliable) >> [c0000007f648fa30] [c0000000001430e0] smp_call_function_any+0x170/0x1c0 >> [c0000007f648fa90] [c0000000007b4b00] >> powernv_cpufreq_target_index+0xe0/0x250 >> [c0000007f648fb00] [c0000000007ac9dc] >> __cpufreq_driver_target+0x20c/0x3d0 >> [c0000007f648fbc0] [c0000000007b1b4c] od_dbs_timer+0xcc/0x260 >> [c0000007f648fc10] [c0000000007b3024] dbs_work_handler+0x54/0xa0 >> [c0000007f648fc50] [c0000000000c49a8] process_one_work+0x1d8/0x590 >> [c0000007f648fce0] [c0000000000c4e08] worker_thread+0xa8/0x660 >> [c0000007f648fd80] [c0000000000cca88] kthread+0x108/0x130 >> [c0000007f648fe30] [c0000000000095e8] ret_from_kernel_thread+0x5c/0x74 >> >> Moving smp_call_function_any() out of the critical section and changing >> irq safe spinlocks to normal spinlocks. >> >> Reported-by: Abdul Haleem <abdhalee@...ux.vnet.linux.com> >> Signed-off-by: Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com> >> --- >> Patch is based on Rafael's linux-next >> drivers/cpufreq/powernv-cpufreq.c | 9 +++++---- >> 1 file changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c >> index 144c732..1f0e20c 100644 >> --- a/drivers/cpufreq/powernv-cpufreq.c >> +++ b/drivers/cpufreq/powernv-cpufreq.c >> @@ -581,9 +581,10 @@ void gpstate_timer_handler(unsigned long data) >> gpstates->last_gpstate = freq_data.gpstate_id; >> gpstates->last_lpstate = freq_data.pstate_id; >> >> + 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); >> - spin_unlock(&gpstates->gpstate_lock); >> } >> >> /* >> @@ -596,7 +597,6 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy, >> { >> struct powernv_smp_call_data freq_data; >> unsigned int cur_msec, gpstate_id; >> - unsigned long flags; >> struct global_pstate_info *gpstates = policy->driver_data; >> >> if (unlikely(rebooting) && new_index != get_nominal_index()) >> @@ -607,7 +607,7 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy, >> >> cur_msec = jiffies_to_msecs(get_jiffies_64()); >> >> - spin_lock_irqsave(&gpstates->gpstate_lock, flags); >> + spin_lock(&gpstates->gpstate_lock); > You don't necessarily have to write 'what you are doing' in the commit log, but > tell us why you are doing that. > > Please explain, why is this changed and why will things continue to work > without this. > Thanks for reviewing. I have tried to convey that in the first line of commit message, "WARN_ON caused by smp_call_function_any() when irq is disabled, because of changes made in the patch" I see, i have not explained why i am changing irq safe spinlock to normal spinlock. will add some explanation.
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