linux-kernel - Re: [PATCH] locktorture: Fix Oops when reader/writer count is 0

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Date:   Wed, 8 Nov 2017 10:57:07 -0600
From:   Jeremy Linton <jeremy.linton@....com>
To:     paulmck@...ux.vnet.ibm.com, Davidlohr Bueso <dave@...olabs.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        josh@...htriplett.org
Subject: Re: [PATCH] locktorture: Fix Oops when reader/writer count is 0

On 11/08/2017 10:48 AM, Paul E. McKenney wrote:
> On Wed, Nov 08, 2017 at 06:45:23AM -0800, Davidlohr Bueso wrote:
>> On Tue, 07 Nov 2017, Paul E. McKenney wrote:
>>
>>> On Tue, Nov 07, 2017 at 10:07:48PM +0100, Peter Zijlstra wrote:
>>>> On Tue, Nov 07, 2017 at 02:01:58PM -0600, Jeremy Linton wrote:
>>>>> Hi,
>>>>>
>>>>> On 10/10/2017 10:52 AM, Jeremy Linton wrote:
>>>>>> If nwriters_stress=0 is passed to the lock torture test
>>>>>> it will panic in:
>>>>>
>>>>> Ping?
>>>>>
>>>>> Has anyone had a chance to look at this?
>>>>
>>>> Helps if you Cc the people actually working on this stuff of course...
>>>
>>> Thank you for the forward, Peter, I have queued Jeremy's patch for
>>> testing and review.
>>
>> fyi I had proposed the following a while back, which I think is more
>> complete than this patch:
>>
>> https://lkml.org/lkml/2017/5/15/201
>>
>> Ah, there's also this (unrelated) fix:
>> https://lkml.org/lkml/2017/5/15/203
>>
>>> But Jeremy's list of email addresses is what you would expect from
>>> looking at MAINTAINERS, so how about the following patch?
> 
> And it looks like Jeremy was not alone -- I was not CCed on either
> of those patches, either.
> 
> Dave's patch does look more complete, and it certainly was submitted
> first.  Let's see if it still applies...  And they both do.

Yes, avoiding the zero length allocations is probably a good plan, and 
complaining if both the reader and writer are zero is doesn't hurt either.

So, I'm good with that patch too..

Reviewed-by: Jeremy Linton <jeremy.linton@....com>

> 
> Jeremy, could you please test Dave's patches and make sure that they
> work for you?  That way I can apply your Tested-by.  Dave, any objection
> to my adding Jeremy's Reported-by to your /201 patch?

I will give it a spin..

> 
> 						Thanx, Paul
> 
>>> ------------------------------------------------------------------------
>>>
>>> commit 58322063498c8f5a3cc88f95bee237a0ce81f70a
>>> Author: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>>> Date:   Tue Nov 7 14:10:03 2017 -0800
>>>
>>>    torture: Place all torture-test modules in one MAINTAINERS group
>>>
>>>    There is some confusion about where patches to kernel/torture.c
>>>    and kernel/locking/locktorture.c should be sent.  This commit
>>>    therefore updates MAINTAINERS appropriately.
>>>
>>>    Reported-by: Peter Zijlstra <peterz@...radead.org>
>>>    Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index 2d3d750b19c0..eab868adedc6 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -8091,6 +8091,7 @@ F:	arch/*/include/asm/rwsem.h
>>> F:	include/linux/seqlock.h
>>> F:	lib/locking*.[ch]
>>> F:	kernel/locking/
>>> +X:	kernel/locking/locktorture.c
>>>
>>> LOGICAL DISK MANAGER SUPPORT (LDM, Windows 2000/XP/Vista Dynamic Disks)
>>> M:	"Richard Russon (FlatCap)" <ldm@...tcap.org>
>>> @@ -11318,15 +11319,6 @@ L:	linux-wireless@...r.kernel.org
>>> S:	Orphan
>>> F:	drivers/net/wireless/ray*
>>>
>>> -RCUTORTURE MODULE
>>> -M:	Josh Triplett <josh@...htriplett.org>
>>> -M:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
>>> -L:	linux-kernel@...r.kernel.org
>>> -S:	Supported
>>> -T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>>> -F:	Documentation/RCU/torture.txt
>>> -F:	kernel/rcu/rcutorture.c
>>> -
>>> RCUTORTURE TEST FRAMEWORK
>>> M:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
>>> M:	Josh Triplett <josh@...htriplett.org>
>>> @@ -13558,6 +13550,18 @@ L:	platform-driver-x86@...r.kernel.org
>>> S:	Maintained
>>> F:	drivers/platform/x86/topstar-laptop.c
>>>
>>> +TORTURE-TEST MODULES
>>> +M:	Davidlohr Bueso <dave@...olabs.net>
>>> +M:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
>>> +M:	Josh Triplett <josh@...htriplett.org>
>>> +L:	linux-kernel@...r.kernel.org
>>> +S:	Supported
>>> +T:	git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>>> +F:	Documentation/RCU/torture.txt
>>> +F:	kernel/torture.c
>>> +F:	kernel/rcu/rcutorture.c
>>> +F:	kernel/locking/locktorture.c
>>
>> Sure, if you think this is the best way to go, I have no problem.
>>
>> Thanks,
>> Davidlohr
>>
>