diff options
author | Todd Poynor <toddpoynor@google.com> | 2012-12-18 17:50:44 -0800 |
---|---|---|
committer | Arve Hjønnevåg <arve@android.com> | 2013-07-01 14:16:18 -0700 |
commit | beb55c19d504f6d8fd7cd1c019027d67d4b4084a (patch) | |
tree | 065f94bb09c24bc12ff6fc32162acc55a6243355 /drivers | |
parent | f5e5ad4292c6ebe1d57221413d8215d024c6c401 (diff) |
cpufreq: interactive: fix racy timer stopping
When stopping the governor, del_timer_sync() can race against an
invocation of the idle notifier callback, which has the potential
to reactivate the timer.
To fix this issue, a read-write semaphore is used. Multiple readers are
allowed as long as pcpu->governor_enabled is true. However it can be
moved to false only after taking a write semaphore which would wait for
any on-going asynchronous activities to complete and prevent any more of
those activities to be initiated.
[toddpoynor@google.com: cosmetic and commit text changes]
Change-Id: Ib51165a735d73dcf964a06754c48bdc1913e13d0
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/cpufreq/cpufreq_interactive.c | 38 |
1 files changed, 28 insertions, 10 deletions
diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c index f8e9ee9f713..74f56093d2f 100644 --- a/drivers/cpufreq/cpufreq_interactive.c +++ b/drivers/cpufreq/cpufreq_interactive.c @@ -21,7 +21,7 @@ #include <linux/cpufreq.h> #include <linux/module.h> #include <linux/moduleparam.h> -#include <linux/mutex.h> +#include <linux/rwsem.h> #include <linux/sched.h> #include <linux/sched/rt.h> #include <linux/tick.h> @@ -29,7 +29,6 @@ #include <linux/timer.h> #include <linux/workqueue.h> #include <linux/kthread.h> -#include <linux/mutex.h> #include <linux/slab.h> #include <asm/cputime.h> @@ -52,6 +51,7 @@ struct cpufreq_interactive_cpuinfo { unsigned int floor_freq; u64 floor_validate_time; u64 hispeed_validate_time; + struct rw_semaphore enable_sem; int governor_enabled; }; @@ -279,8 +279,8 @@ static void cpufreq_interactive_timer(unsigned long data) unsigned long flags; bool boosted; - smp_rmb(); - + if (!down_read_trylock(&pcpu->enable_sem)) + return; if (!pcpu->governor_enabled) goto exit; @@ -387,6 +387,7 @@ rearm: cpufreq_interactive_timer_resched(pcpu); exit: + up_read(&pcpu->enable_sem); return; } @@ -396,8 +397,12 @@ static void cpufreq_interactive_idle_start(void) &per_cpu(cpuinfo, smp_processor_id()); int pending; - if (!pcpu->governor_enabled) + if (!down_read_trylock(&pcpu->enable_sem)) + return; + if (!pcpu->governor_enabled) { + up_read(&pcpu->enable_sem); return; + } pending = timer_pending(&pcpu->cpu_timer); @@ -414,6 +419,7 @@ static void cpufreq_interactive_idle_start(void) cpufreq_interactive_timer_resched(pcpu); } + up_read(&pcpu->enable_sem); } static void cpufreq_interactive_idle_end(void) @@ -421,8 +427,12 @@ static void cpufreq_interactive_idle_end(void) struct cpufreq_interactive_cpuinfo *pcpu = &per_cpu(cpuinfo, smp_processor_id()); - if (!pcpu->governor_enabled) + if (!down_read_trylock(&pcpu->enable_sem)) + return; + if (!pcpu->governor_enabled) { + up_read(&pcpu->enable_sem); return; + } /* Arm the timer for 1-2 ticks later if not already. */ if (!timer_pending(&pcpu->cpu_timer)) { @@ -432,6 +442,8 @@ static void cpufreq_interactive_idle_end(void) del_timer(&pcpu->cpu_slack_timer); cpufreq_interactive_timer(smp_processor_id()); } + + up_read(&pcpu->enable_sem); } static int cpufreq_interactive_speedchange_task(void *data) @@ -466,10 +478,12 @@ static int cpufreq_interactive_speedchange_task(void *data) unsigned int max_freq = 0; pcpu = &per_cpu(cpuinfo, cpu); - smp_rmb(); - - if (!pcpu->governor_enabled) + if (!down_read_trylock(&pcpu->enable_sem)) + continue; + if (!pcpu->governor_enabled) { + up_read(&pcpu->enable_sem); continue; + } for_each_cpu(j, pcpu->policy->cpus) { struct cpufreq_interactive_cpuinfo *pjcpu = @@ -486,6 +500,8 @@ static int cpufreq_interactive_speedchange_task(void *data) trace_cpufreq_interactive_setspeed(cpu, pcpu->target_freq, pcpu->policy->cur); + + up_read(&pcpu->enable_sem); } } @@ -936,10 +952,11 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy, case CPUFREQ_GOV_STOP: for_each_cpu(j, policy->cpus) { pcpu = &per_cpu(cpuinfo, j); + down_write(&pcpu->enable_sem); pcpu->governor_enabled = 0; - smp_wmb(); del_timer_sync(&pcpu->cpu_timer); del_timer_sync(&pcpu->cpu_slack_timer); + up_write(&pcpu->enable_sem); } if (atomic_dec_return(&active_count) > 0) @@ -989,6 +1006,7 @@ static int __init cpufreq_interactive_init(void) init_timer(&pcpu->cpu_slack_timer); pcpu->cpu_slack_timer.function = cpufreq_interactive_nop_timer; spin_lock_init(&pcpu->load_lock); + init_rwsem(&pcpu->enable_sem); } spin_lock_init(&target_loads_lock); |