On Sun, 7 Jan 2007 16:30:13 +0530 Srivatsa Vaddagiri <[EMAIL PROTECTED]> wrote:
> On Sat, Jan 06, 2007 at 11:11:17AM -0800, Andrew Morton wrote: > > Has anyone thought seriously about using the process freezer in the > > cpu-down/cpu-up paths? That way we don't need to lock anything anywhere? > > How would this provide a stable access to cpu_online_map in functions > that need to block while accessing it (as flush_workqueue requires)? If a thread simply blocks, that will not permit a cpu plug/unplug to proceed. The thread had to explicitly call try_to_freeze(). CPU plug/unplug will not occur (and cpu_online_map will not change) until every process in the machine has called try_to_freeze()). So the problem which you're referring to will only occur if a workqueue callback function calls try_to_freeze(), which would be mad. Plus flush_workqueue() is on the way out. We're slowly edging towards a working cancel_work() which will only block if the work which you're trying to cancel is presently running. With that, pretty much all the flush_workqueue() calls go away, and all these accidental rarely-occurring deadlocks go away too. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
