On 03/19/2014 07:05 PM, Viresh Kumar wrote: > On 19 March 2014 17:45, Srivatsa S. Bhat > <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: >> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h >> + bool transition_ongoing; /* Tracks transition status */ >> + struct mutex transition_lock; >> + wait_queue_head_t transition_wait; > > Similar to what I have done in my last version, why do you need > transition_ongoing and transition_wait? Simply work with > transition_lock? i.e. Acquire it for the complete transition sequence. > We *can't* acquire it for the complete transition sequence in case of drivers that do asynchronous notification, because PRECHANGE is done in one thread and POSTCHANGE is done in a totally different thread! You can't acquire a lock in one task and release it in a different task. That would be a fundamental violation of locking. That's why I introduced the wait queue to help us create a "flow" which encompasses 2 different, but co-ordinating tasks. You simply can't do that elegantly by using plain locks alone. Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
