On Fri, 2013-04-19 at 14:47 +0200, Frederic Weisbecker wrote: > > > > > I might be mistaken but I believe that firing timers are not rescheduled > > in the current interrupt context. They are going to be rescheduled later > > from the task context handling the timer generated signal. > > No, when the timer fires, it might generate a signal. But it won't > execute that signal right away in the same code path. Instead, after > signal generation, it may reschedule the timer if necessary then look > at the next firing timer in the list. This is all made from the same > timer interrupt context from the same call to run_posix_cpu_timers(). > The signal itself is executed asynchronously. Either by interrupting a > syscall, or from the irq return path. > Frederic, be careful with the interpretation, there are 2 locations from where posix_cpu_timer_schedule() can be called.
Call to posix_cpu_timer_schedule() from cpu_timer_fire() only happens if the signal isn't sent because it is ignored by the recipient. Maybe the condition around the posix_cpu_timer_schedule() block inside cpu_timer_fire() could even be a good candidate for 'unlikely' qualifier. IMO, a more likely scenario, posix_cpu_timer_schedule() will be called from dequeue_signal() which will be from from a different context than the interrupt context. At best, you have an interesting race! dequeue_signal() is called when delivering a signal, not when it is generated, right? If you have a different understanding then please explain when call to posix_cpu_timer_schedule() from dequeue_signal() will happen. -- 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/
