diff options
author | Akshay Adiga <akshay.adiga@linux.vnet.ibm.com> | 2016-05-03 20:49:35 +0530 |
---|---|---|
committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-05-11 02:28:00 +0200 |
commit | 1fd3ff2874f79c04354f3e80e583afbe6fa6eaa2 (patch) | |
tree | becbe005d5bec27dbee82f07446b7f713b0df74b /drivers | |
parent | f96fd0c86f081c27a0ba5efadfc13f612b4071d3 (diff) |
cpufreq: powernv: Move smp_call_function_any() out of irq safe block
Fix 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
- Calling smp_call_function_any() with interrupt disabled (through
spin_lock_irqsave) could cause a deadlock, as smp_call_function_any()
relies on the IPI to complete. This is detected in the
smp_call_function_any() call and hence the WARN_ON.
- As the spinlock (gpstates->lock) is only used to synchronize access of
global_pstate_info between timer irq handler and target_index calls. And
the timer irq handler just try_locks() hence it would not cause a
deadlock. Hence could do without making spinlocks irq safe.
- As the smp_call_function_any() is a blocking call and does not access
global_pstates_info, it could reduce the critcal section by moving
smp_call_function_any() after giving up the lock.
Reported-by: Abdul Haleem <abdhalee@linux.vnet.linux.com>
Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/cpufreq/powernv-cpufreq.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index 144c73211926..1f0e20ccc2ff 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); freq_data.pstate_id = powernv_freqs[new_index].driver_data; if (!gpstates->last_sampled_time) { @@ -654,13 +654,14 @@ gpstates_done: gpstates->last_gpstate = freq_data.gpstate_id; gpstates->last_lpstate = freq_data.pstate_id; + spin_unlock(&gpstates->gpstate_lock); + /* * Use smp_call_function to send IPI and execute the * mtspr on target CPU. We could do that without IPI * if current CPU is within policy->cpus (core) */ smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1); - spin_unlock_irqrestore(&gpstates->gpstate_lock, flags); return 0; } |