Andrew, please drop the workqueue-rework-threads-hotplug-management.patch, and please take this one (feel free to just kill me instead).
We have workqueue callbacks (slab for example) which assume that CPU is stable during the execution since cwq->thread is pinned to a processor. With or without that patch this is not true with CONFIG_HOTPLUG_CPU, and the problem is not connected to workqueue.c. However, my patch makes the things worse, because CPU_UP_PREPARE creates cwq->thread which is not pinned to CPU until CPU_ONLINE. This is solvable, but needs a serious complication, so this patch can't be considered as a cleanup. The new patch removes take_over_work() and friends (as the old one did), but retains an unfortunate property of the current implementation: the workqueue_mutex is held from CPU_LOCK_ACQUIRE to CPU_LOCK_RELEASE, and CPU_DEAD stops cwq->thread synchronously. This means that cpu-hotplug callbacks can't create/destroy workqueues (Gautham needs this?), and work->func() can't share a lock with cpu hotplug. May be we can change this later, but this needs a separate patch. Srivatsa, do you have any objections? The new patch is very similar (in fact, a subset), I don't send incremental update because this will break changelogs. Oleg. - 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/
