On 08-12-15, 17:42, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > Subject: [PATCH] cpufreq: governor: Use lockless timer function > > It is possible to get rid of the timer_lock spinlock used by the > governor timer function for synchronization, but a couple of races > need to be avoided. > > The first race is between multiple dbs_timer_handler() instances > that may be running in parallel with each other on different > CPUs. Namely, one of them has to queue up the work item, but it > cannot be queued up more than once. To achieve that, > atomic_inc_return() can be used on the skip_work field of > struct cpu_common_dbs_info. > > The second race is between an already running dbs_timer_handler() > and gov_cancel_work(). In that case the dbs_timer_handler() might > not notice the skip_work incrementation in gov_cancel_work() and > it might queue up its work item after gov_cancel_work() had > returned (and that work item would corrupt skip_work going > forward). To prevent that from happening, gov_cancel_work() > can be made wait for the timer function to complete (on all CPUs) > right after skip_work has been incremented. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > --- > drivers/cpufreq/cpufreq_governor.c | 49 > ++++++++++++++++--------------------- > drivers/cpufreq/cpufreq_governor.h | 9 +----- > 2 files changed, 24 insertions(+), 34 deletions(-)
Acked-by: Viresh Kumar <viresh.ku...@linaro.org> -- viresh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
