lkml.org 
[lkml]   [2009]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: NMI between switch_mm and switch_to
    From
    Date
    On Tue, 2009-07-28 at 14:49 +1000, Paul Mackerras wrote:
    > Ben H. suggested there might be a problem if we get a PMU interrupt
    > and try to do a stack trace of userspace in the interval between when
    > we call switch_mm() from sched.c:context_switch() and when we call
    > switch_to(). If we get an NMI in that interval and do a stack trace
    > of userspace, we'll see the registers of the old task but when we peek
    > at user addresses we'll see the memory image for the new task, so the
    > stack trace we get will be completely bogus.
    >
    > Is this in fact also a problem on x86, or is there some subtle reason
    > why it can't happen there?

    I can't spot one, maybe Ingo can when he's back :-)

    So I think this is very good spotting from Ben.

    We could use preempt notifiers (or put in our own hooks) to disable
    callchains during the context switch I suppose.



    \
     
     \ /
      Last update: 2009-07-28 09:51    [W:0.024 / U:32.812 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site