Messages in this thread | | | Date | Thu, 1 Sep 2005 14:09:38 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH]kprobes fix bug when probed on task and isr functions |
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Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com> wrote: > > This patch fixes a race condition where in system used to hang > or sometime crash within minutes when kprobes are inserted on > ISR routine and a task routine.
It's desirable that the patch descriptions tell us _how_ a bug was fixed, as well as what the bug was. It means that people don't have to ask questions like:
> void __kprobes lock_kprobes(void) > { > + unsigned long flags = 0; > + > + local_irq_save(flags); > spin_lock(&kprobe_lock); > kprobe_cpu = smp_processor_id(); > + local_irq_restore(flags); > }
what is this change trying to do? If a lock is taken from both process and irq contexts then local IRQs must be disabled for the entire period when the lock is held, not just for a little blip like this. If IRQ-context code is running this function then the code is deadlockable.
Now, probably there's deep magic happening here and I'm wrong. If so then please explain the code's magic via a comment patch so the question doesn't arise again, thanks.
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