linux-kernel - Re: [tip:tmp.tmp] [sched/fair] eb2db043ab: BUG:kernel_NULL_pointer

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Message-ID: <aS/enCbsTTlXiAEL@xsang-OptiPlex-9020>
Date: Wed, 3 Dec 2025 14:54:20 +0800
From: Oliver Sang <oliver.sang@...el.com>
To: Ingo Molnar <mingo@...nel.org>
CC: Peter Zijlstra <peterz@...radead.org>, Tim Chen
	<tim.c.chen@...ux.intel.com>, <oe-lkp@...ts.linux.dev>, <lkp@...el.com>,
	<linux-kernel@...r.kernel.org>, <x86@...nel.org>, Chen Yu
	<yu.c.chen@...el.com>, Vincent Guittot <vincent.guittot@...aro.org>,
	Shrikanth Hegde <sshegde@...ux.ibm.com>, K Prateek Nayak
	<kprateek.nayak@....com>, Srikar Dronamraju <srikar@...ux.ibm.com>, "Mohini
 Narkhede" <mohini.narkhede@...el.com>, <aubrey.li@...ux.intel.com>
Subject: Re: [tip:tmp.tmp] [sched/fair]  eb2db043ab:
 BUG:kernel_NULL_pointer_dereference,address

hi, Ingo Molnar, hi, Peter Zijlstra,

On Tue, Dec 02, 2025 at 06:11:36AM +0100, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Fri, Nov 28, 2025 at 09:42:04AM +0800, Oliver Sang wrote:
> > > hi,
> > > 
> > > On Thu, Nov 27, 2025 at 10:07:28AM +0100, Ingo Molnar wrote:
> > > > 
> > > > * Peter Zijlstra <peterz@...radead.org> wrote:
> > > > 
> > > > > On Thu, Nov 27, 2025 at 04:35:37PM +0800, kernel test robot wrote:
> > > > > > 
> > > > > > 
> > > > > > Hello,
> > > > > > 
> > > > > > kernel test robot noticed "BUG:kernel_NULL_pointer_dereference,address" on:
> > > > > > 
> > > > > > commit: eb2db043ab3a28ae76800f2a57e144420800d56d ("sched/fair: Skip sched_balance_running cmpxchg when balance is not due")
> > > > > > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git tmp.tmp
> > > > > 
> > > > > Not sure what this branch is, but tip/sched/core has the fixed commit.
> > > > 
> > > > Not sure how the test-bot picked up this temporary 
> > > > branch and reported it despite it being gone from the 
> > > > repo, but the branch hasn't been in -tip for days.
> > > > 
> > > > This report can be safely ignored.
> > > 
> > > sorry for the noise. yeah, our so-called 'gitmirror' mechnism fetched the
> > > tmp.tmp branch about 10 days ago, then it merged into our hourly kernel to
> > > be running tests. so it's kind of 'stored' in our repo.
> > > 
> > > since the bad commit caused crash issue on various test machines, we made out
> > > the report, but missed the check of whether branch is still existing remotely.
> > > 
> > > we will refine our code/process to avoid this kind of meaningless report.
> > 
> > Might it make sense to exclude all branches named tmp ?
> 
> So the tmpfs project might disagree. ;-)
> 
> But a '^tmp\.' prefix exclusion pattern should be 
> pretty robust IMO.
> 
> > [...] IIRC there are some patterns that the robot 
> > skips over, but I forever forget what they are :/
> 
> I'm curious about those patterns, although 99% of the 
> time I'm *happy* when the LKP robot finds a new 
> development branch that I pushed out, quite often it 
> will find bugs that my own testing doesn't catch, and 
> the reports are useful & relevant these days. Beyond 
> the bugreports the 'SUCCESS' reports are useful as 
> well, as they can be used to phase the flow of 
> development commits. So no complaints from me.
> 
> This tmp.tmp case was an exception to the rule really, 
> and given the overwhelmingly positive net utility of 
> the LKP test-bot I'd just ignore it, especially since 
> the LKP bot was technically correct and the crashes 
> were real (albeit fixed already).

we do have some default pattern for branches to ignore:
default_branch_denylist: (.*experimental.*|.*dont-build|origin/.*|remotes/.*|.*/orphan-.*)
(https://github.com/intel/lkp-tests/blob/master/repo/linux/DEFAULTS#L5)

but we also support repo specific configurations. such like for tip:
branch_denylist: auto-.*|tmp.*|base-.*|test.*|.*-for-linus|tip
(https://github.com/intel/lkp-tests/blob/master/repo/linux/tip#L19)

the "tmp.*" is just updated from previous "tmp-.*" to cover tmp.tmp
(https://github.com/intel/lkp-tests/commit/acd36193a0dd2bbc1c6d4ef59dd2b33a2eece3e0)

thanks

> 
> Thanks,
> 
> 	Ingo
>