Re: [local DoS] Re: Linux 2.6.24-rc4

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From: Luiz Fernando N. Capitulino
Date: Tuesday, December 4, 2007 - 9:04 am

Em Tue, 4 Dec 2007 17:00:05 +0100
Ingo Molnar <mingo@elte.hu> escreveu:

| 
| * Linus Torvalds <torvalds@linux-foundation.org> wrote:
| 
| > 
| > 
| > On Tue, 4 Dec 2007, Luiz Fernando N. Capitulino wrote:
| > >
| > > 	sched_rr_get_interval(1, NULL);
| > 
| > Looks like we have a zero "cfs_rq->load.weight".
| > 
| > Ingo? Both sched_slice() and __sched_slice() do a divide by the 
| > runqueue weight, and at least dequeue_task_fair() explicitly checks 
| > for that being zero, so clearly zero is a possible value. Hmm?
| 
| yeah, i can reproduce this crash too.
| 
| The problem is on SMP: if sched_rr_get_interval() gets a task from an 
| otherwise idle runqueue, then rq->load.weight is 0. Normally 
| sched_slice() is only used on a busy runqueue. So the correct fixup site 
| is not in sched_slice() but in sys_sched_rr_get_interval() - i'm working 
| on the right fix, i hope to be able to send a pull request in a few 
| minutes.

 Ingo, I can reproduce this w/o SMP support as well.

 (Also, the backtrace I sent was reproduced on a UP machine with a
SMP kernel).

-- 
Luiz Fernando N. Capitulino
--
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Messages in current thread:
Linux 2.6.24-rc4, Linus Torvalds, (Mon Dec 3, 10:08 pm)
[build failure] Re: Linux 2.6.24-rc4 on S390x, Kamalesh Babulal, (Tue Dec 4, 3:23 am)
Re: [build failure] Re: Linux 2.6.24-rc4 on S390x, Martin Schwidefsky, (Tue Dec 4, 3:31 am)
Re: [build failure] Re: Linux 2.6.24-rc4 on S390x, Ingo Molnar, (Tue Dec 4, 3:32 am)
Re: Linux 2.6.24-rc4, Nicolas Pitre, (Tue Dec 4, 6:22 am)
[local DoS] Re: Linux 2.6.24-rc4, Luiz Fernando N. Cap ..., (Tue Dec 4, 7:07 am)
Re: [local DoS] Re: Linux 2.6.24-rc4, Linus Torvalds, (Tue Dec 4, 8:56 am)
Re: Linux 2.6.24-rc4, Jeff Garzik, (Tue Dec 4, 9:04 am)
Re: [local DoS] Re: Linux 2.6.24-rc4, Luiz Fernando N. Cap ..., (Tue Dec 4, 9:04 am)
Re: [local DoS] Re: Linux 2.6.24-rc4, Ingo Molnar, (Tue Dec 4, 9:08 am)
[git pull] scheduler fixes, Ingo Molnar, (Tue Dec 4, 9:18 am)
Re: [git pull] scheduler fixes, Luiz Fernando N. Cap ..., (Tue Dec 4, 9:40 am)
Re: [git pull] scheduler fixes, Greg KH, (Tue Dec 4, 11:28 am)
Re: [git pull] scheduler fixes, Luiz Fernando N. Cap ..., (Tue Dec 4, 11:41 am)
Re: Linux 2.6.24-rc4, Diego Calleja, (Tue Dec 4, 5:23 pm)