Messages in this thread |  | | Date | Thu, 20 Feb 2003 10:01:15 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: doublefault debugging (was Re: Linux v2.5.62 --- spontaneous reboots) |
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On Thu, 20 Feb 2003, Ingo Molnar wrote: > > a true heisenbug. I cannot reproduce it anymore. Anyway, from the serial > console i collected 3 instances of crashes - whatever it's worth.
Pretty much every single time, release_task() has been there on the backtrace.
In fact, I bet you this code in do_exit() is the cause:
preempt_disable();
if (tsk->exit_signal == -1) *** release_task(tsk); ***
schedule();
Note how "release_task()" will be releasing the stack that the process is running on right now. And the reason it doesn't crash _every_ time is simply that you need to have:
- another memory allocation that picks up that page and fills it with something else in order to get a corrupted stack - and something delays schedule() so that you have time to race _and_ you need the stack. Which is why most of the oopses have an interrupt come in inside schedule (see the "common_interrupt()" thing
In other words, I think we need to have schedule_tail() do the release_task(), otherwise we'd release it too early while the task structure (and the stack) are both still in use.
You owe me a patch.
Linus
---
> [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c010a594>] common_interrupt+0x18/0x20 > [<c010a691>] error_code+0x2d/0x38 > [<c011b881>] schedule+0x3a1/0x3d0 > [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c010bc28>] handle_IRQ_event+0x38/0x60 > [<c010bf6b>] do_IRQ+0x14b/0x1e0 > [<c010a594>] common_interrupt+0x18/0x20 > [<c010a691>] error_code+0x2d/0x38 > [<c011b881>] schedule+0x3a1/0x3d0 > [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c010bf6b>] do_IRQ+0x14b/0x1e0 > [<c010a594>] common_interrupt+0x18/0x20 > [<c010a691>] error_code+0x2d/0x38 > [<c011b881>] schedule+0x3a1/0x3d0 > [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c010bf6b>] do_IRQ+0x14b/0x1e0 > [<c010a594>] common_interrupt+0x18/0x20 > [<c010a691>] error_code+0x2d/0x38 > [<c011b881>] schedule+0x3a1/0x3d0 > [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c011e06c>] __put_task_struct+0x7c/0x90 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c010bc28>] handle_IRQ_event+0x38/0x60 > [<c010bf6b>] do_IRQ+0x14b/0x1e0 > [<c010a594>] common_interrupt+0x18/0x20 > [<c010a691>] error_code+0x2d/0x38 > [<c011b881>] schedule+0x3a1/0x3d0 > [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
> [<c010bc28>] handle_IRQ_event+0x38/0x60 > [<c010bf6b>] do_IRQ+0x14b/0x1e0 > [<c010a594>] common_interrupt+0x18/0x20 > [<c010a691>] error_code+0x2d/0x38 > [<c011b881>] schedule+0x3a1/0x3d0 > [<c01219fd>] release_task+0x17d/0x200 > [<c011e70f>] mmput+0x1f/0xc0 > [<c0122cad>] do_exit+0x31d/0x3b0
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