Mathieu Desnoyers wrote: > > This patch adds the ability to protect critical sections from migration to > another CPU without disabling preemption. > > Typical use: > > migration_disable(); > local_inc(&__get_cpu_var(&my_local_t_var)); > migration_enable(); > > --- linux-2.6-lttng.orig/kernel/sched.c 2007-07-05 16:28:15.000000000 > -0400 > +++ linux-2.6-lttng/kernel/sched.c 2007-07-05 16:53:24.000000000 -0400 > @@ -1996,6 +1996,7 @@ > * 1) running (obviously), or > * 2) cannot be migrated to this CPU due to cpus_allowed, or > * 3) are cache-hot on their current CPU. > + * 4) migration preemption is non 0 for this non running task. > */ > if (!cpu_isset(this_cpu, p->cpus_allowed)) > return 0; > @@ -2003,6 +2004,8 @@ > > if (task_running(rq, p)) > return 0; > + if (task_thread_info(p)->migration_count) > + return 0;
Question: This means that the task could be preempted, but can't sleep, yes? Because try_to_wake_up() can change ->cpu. Shouldn't might_sleep() check ->migration_count then? Or we can change try_to_wake_up(). What if the task does copy_process() under migration_disable() ? Child gets a copy of ->migration_count. Also, cpu_down() still can migrate this task to another CPU. 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/
