Re: frequent lockups in 3.18rc4
From: Dave Jones
Date: Tue Dec 02 2014 - 14:32:22 EST
On Mon, Dec 01, 2014 at 12:36:34PM -0800, Linus Torvalds wrote:
> On Mon, Dec 1, 2014 at 12:28 PM, Dâniel Fraga <fragabr@xxxxxxxxx> wrote:
> > Hi Paul. Please, I'd like the patch, because without
> > preemption, I'm unable to trigger this bug.
> Ok, that's already interesting information. And yes, it would probably
> be interesting to see if CONFIG_PREEMPT=y but !CONFIG_TREE_PREEMPT_RCU
> then solves it too, to narrow it down to one but not the other..
> DaveJ - what about your situation? The standard Fedora kernels use
> CONFIG_PREEMPT_VOLUNTARY, do you have CONFIG_PREEMPT and
> CONFIG_TREE_PREEMPT_RCU enabled?
I periodically switch PREEMPT options, just to see if anything new falls
out, though I've been on CONFIG_PREEMPT for quite a while.
So right now I'm testing the TREE_PREEMPT_RCU case.
I'm in the process of bisecting 3.16 -> 3.17 (currently on -rc1)
Thanksgiving kind of screwed up my flow, but 3.16 got a real
pounding for over 3 days with no problems.
I can give a !PREEMPT_RCU build a try, in case that turns out to
point to something quicker than a bisect is going to.
> I think you and Sasha both saw some RCU oddities too, no?
I don't recall a kernel where I didn't see RCU oddities of some
description, but in recent times, not so much, though a few releases
back I did change some of the RCU related CONFIG options while
Paul & co were chasing down some bugs.
These days I've been running with..
# RCU Subsystem
# CONFIG_TASKS_RCU is not set
# CONFIG_RCU_USER_QS is not set
# CONFIG_RCU_FANOUT_EXACT is not set
# CONFIG_RCU_NOCB_CPU_NONE is not set
# CONFIG_RCU_NOCB_CPU_ZERO is not set
# RCU Debugging
# CONFIG_RCU_TORTURE_TEST is not set
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