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

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Date:   Thu, 9 Nov 2017 10:15:54 -0600
From:   Jeremy Linton <jeremy.linton@....com>
To:     paulmck@...ux.vnet.ibm.com
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        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

Hi,

On 11/08/2017 11:44 AM, Paul E. McKenney wrote:
> On Wed, Nov 08, 2017 at 10:57:07AM -0600, Jeremy Linton wrote:
>> 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>
> 
> Thank you!
> 
>>> 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..
> 
> Very good!  Looking forward to seeing the results.

I've been testing it on arm64 machines and it appears to work as expected.

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

Thanks,


> 
> 					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
>>>>
>>>
>>
>