Messages in this thread Patch in this message | | | Date | Thu, 16 Oct 2003 10:10:45 -0700 | From | "Paul E. McKenney" <> | Subject | Re: OK to set PF_MEMDIE on cleanup tasks? |
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Hello, Andrew,
On Tue, Oct 14, 2003 at 05:12:27PM -0700, Andrew Morton wrote: > > So... Is it considered legit to simply set PF_MEMDIE when creating > > the cleanup task? Or is there some reason that one should deal with > > signal 15? > > Well it's all very unconventional. Catching SIGTERM seems like a suitable > way to do what you want to do.
OK, since this particular case is a strictly in-kernel task, SIGTERM should be a no-op anyway. Unless I am missing something in the signal delivery code, which is quite probable. ;-)
So the magic code would then be:
cap_raise(current->cap_effective, CAP_SYS_RAWIO);
perhaps with:
cap_raise(current->cap_effective, CAP_SYS_ADMIN);
thrown in for good measure.
> Possibly your special process should also run as PF_MEMALLOC. I've seen > that done before, with success. There is no existing API with which this > can be set.
This would certainly head off at least some OOM deadlock situations. On the (perhaps unlikely) chance that this was an invitation, here is a patch to create an API.
Thanx, Paul
diff -urN -X /home/linux/2.5/dontdiff linux-2.6.0-test7-mm1/include/linux/sched.h linux-2.6.0-test7-mm1-PF_MEMALLOC/include/linux/sched.h --- linux-2.6.0-test7-mm1/include/linux/sched.h 2003-10-16 07:16:05.000000000 -0700 +++ linux-2.6.0-test7-mm1-PF_MEMALLOC/include/linux/sched.h 2003-10-16 09:20:34.000000000 -0700 @@ -508,6 +508,27 @@ #define PF_LESS_THROTTLE 0x00100000 /* Throttle me less: I clean memory */ #define PF_SYNCWRITE 0x00200000 /* I am doing a sync write */ +/** + * mark_task_memalloc - mark the specified task as deserving of preferential + * access to free memory. Note that with great power comes great + * responsibility. + * @p: the task structure to be granted preferential access. + */ +static inline void mark_task_memalloc(task_t *p) +{ + p->flags |= PF_MEMALLOC; +} + +/** + * unmark_task_memalloc - mark the specified task as no longer deserving + * of preferential access to free memory. + * @p: the task structure to have its preferential access revoked. + */ +static inline void unmark_task_memalloc(task_t *p) +{ + p->flags &= ~PF_MEMALLOC; +} + #ifdef CONFIG_SMP extern int set_cpus_allowed(task_t *p, cpumask_t new_mask); #else - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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