* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 26 Jan 2009 23:05:37 +0100 > Ingo Molnar <mingo@xxxxxxx> wrote: > > > > > * Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > Well it turns out that I was having a less-than-usually-senile moment: > > > > > > : implement flush_work() > > > > > Why isn't that working in this case?? > > > > how would that work in this case? We defer processing into the workqueue > > exactly because we want its per-CPU properties. > > It detaches the work item, moves it to head-of-queue, reinserts it then > waits on it. I think. > > This might have a race+hole. If a currently-running "unrelated" work > item tries to take the lock which the flush_work() caller is holding > then there's no way in which keventd will come back to execute the work > item which we just put on the head of queue. Correct - or the unrelated worklet might also be blocked on something - so the window is rather large. > > We want work_on_cpu() to be done in the workqueue context on the CPUs > > that were specified, not in the local CPU context. > > flush_work() is supposed to work in the way which you describe. > > But Oleg's "we may be running on a different CPU" comment has me all > confused. well, we call this on any arbitrary CPU: long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) To execute fn() on 'cpu'. We converted wacky callers that did direct p->cpus_allowed twiddling (and on-stack saving) and set_cpus_allowed() calls to this elegant-looking work_on_cpu() call which just promised exactly this functionality but cleanly so. Ingo -- 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
