Messages in this thread Patch in this message |  | | | Subject | [PATCH] introduce idle_task_exit | | From | Nathan Lynch <> | | Date | Fri, 07 Jan 2005 15:43:09 -0600 |
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On Fri, 2005-01-07 at 05:43, Ingo Molnar wrote: > * Nathan Lynch <nathanl@austin.ibm.com> wrote: > > > OK, how's this? I'll submit the sched and ppc64 bits separately if > > there are no objections. I assume Heiko can take care of s390. > > > > Note that in the ppc64 cpu_die function we must call idle_task_exit > > before calling ppc_md.cpu_die, because the latter does not return. > > Signed-off-by: Ingo Molnar <mingo@elte.hu>
Heiko Carstens figured out that offlining a cpu can leak mm_structs because the dying cpu's idle task fails to switch to init_mm and mmdrop its active_mm before the cpu is down. This patch introduces idle_task_exit, which allows the idle task to do this as Ingo suggested.
I will follow this up with a patch for ppc64 which calls idle_task_exit from cpu_die.
Signed-off-by: Nathan Lynch <nathanl@austin.ibm.com>
---
diff -puN kernel/sched.c~sched-idle_task_exit kernel/sched.c --- linux-2.6.10-bk10/kernel/sched.c~sched-idle_task_exit 2005-01-07 15:23:35.000000000 -0600 +++ linux-2.6.10-bk10-nathanl/kernel/sched.c 2005-01-07 15:23:35.000000000 -0600 @@ -3996,6 +3996,20 @@ void sched_idle_next(void) spin_unlock_irqrestore(&rq->lock, flags); } +/* Ensures that the idle task is using init_mm right before its cpu goes + * offline. + */ +void idle_task_exit(void) +{ + struct mm_struct *mm = current->active_mm; + + BUG_ON(cpu_online(smp_processor_id())); + + if (mm != &init_mm) + switch_mm(mm, &init_mm, current); + mmdrop(mm); +} + static void migrate_dead(unsigned int dead_cpu, task_t *tsk) { struct runqueue *rq = cpu_rq(dead_cpu); diff -puN include/linux/sched.h~sched-idle_task_exit include/linux/sched.h --- linux-2.6.10-bk10/include/linux/sched.h~sched-idle_task_exit 2005-01-07 15:23:35.000000000 -0600 +++ linux-2.6.10-bk10-nathanl/include/linux/sched.h 2005-01-07 15:23:35.000000000 -0600 @@ -757,6 +757,7 @@ extern void sched_exec(void); #endif extern void sched_idle_next(void); +extern void idle_task_exit(void); extern void set_user_nice(task_t *p, long nice); extern int task_prio(const task_t *p); extern int task_nice(const task_t *p); _
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