Messages in this thread |  | | Subject | Re: [PATCH] BUG(): sched.c: Line 944 | From | Robert Love <> | Date | 17 Sep 2002 14:27:52 -0400 |
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On Tue, 2002-09-17 at 05:57, Ingo Molnar wrote:
> We *must* use the schedule() check to debug preemption bugs, or we wont > have usable preemption in 2.6, i dont really understand why your are not > happy that we have such a great tool. In fact we should also add other > debugging bits, like 'check for !0 preemption count in smp_processor_id()' > , and the underflow checks that caught the IDE bug. These are all bits > that help the elimination of preemption bugs which are also often SMP > bugs, on plain UP boxes.
Hm, sorry if I sound like I do not want something "so great". I do. I just do not ever want to compromise the existing code... I would much prefer to say "wow we cannot do this cleanly now, let's wait until we figure out a clean way".
Anyhow, one of us is confused. How can this in_atomic() test _ever_ catch a preemption bug? We cannot enter the scheduler off kernel preemption unless preempt_count==0. This is a test to catch bugs in other parts of the kernel, e.g. where code explicitly calls schedule() while holding a lock.
Robert Love
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