On Fri, Oct 24, 2014 at 11:07:46AM -0400, Burke Libbey wrote: > From 2014-02-15: https://lkml.org/lkml/2014/2/15/217 > > This issue was reported and patched, but it still occurs in some situations on > newer kernel versions. > > [2249353.328452] BUG: unable to handle kernel NULL pointer dereference at > 0000000000000150 > [2249353.336528] IP: [<ffffffff810b1cf7>] check_preempt_wakeup+0xe7/0x210 > > se.parent gets out of sync with se.depth, causing a panic when the algorithm > in > find_matching_se assumes they are correct. This patch forces se.depth to be > updated every time se.parent is, so they can no longer become desync'd. > > CC: Ingo Molnar <[email protected]> > CC: Peter Zijlstra <[email protected]> > Signed-off-by: Burke Libbey <[email protected]> > --- > > I haven't been able to isolate the problem. Though I'm pretty confident this > fixes the issue I've been having, I have not been able to prove it.
So this isn't correct, switching rq should not change depth. I suspect you're just papering over the issue by frequently resetting the value, which simply narrows the race window. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
