Re: [sparc64] locking/atomic, kernel OOPS on running stress-ng

[Mark Rutland]

On Mon, Jul 05, 2021 at 08:56:54PM +0100, Mark Rutland wrote:
> On Mon, Jul 05, 2021 at 06:16:49PM +0300, Anatoly Pugachev wrote:
> > Hello!
> 
> Hi Anatoly,
> 
> > latest sparc64 git kernel produces the following OOPS on running stress-ng as :
> > 
> > $ stress-ng -v --mmap 1 -t 30s
> > 
> > kernel OOPS (console logs):
> > 
> > [   27.276719] Unable to handle kernel NULL pointer dereference
> > [   27.276782] tsk->{mm,active_mm}->context = 00000000000003cb
> > [   27.276818] tsk->{mm,active_mm}->pgd = fff800003a2a0000
> > [   27.276853]               \|/ ____ \|/
> > [   27.276853]               "@'/ .. \`@"
> > [   27.276853]               /_| \__/ |_\
> > [   27.276853]                  \__U_/
> > [   27.276927] stress-ng(928): Oops [#1]
> 
> I can reproduce this under QEMU; following your bisection (and working
> around the missing ifdeferry that breaks bisection), I can confirm that
> the first broken commit is:
> 
>   ff5b4f1ed580 ("locking/atomic: sparc: move to ARCH_ATOMIC")
> 
> Sorry about this.
>  
> > Can someone please look at this commit ids?
> 
> From digging into this, I can't spot an obvious bug in the commit above.

Looking again with fresh eyes, there is a trivial bug after all.

Could you give the patch below a spin? It works for me locally under
QEMU.

Sorry again about this!

Thanks,
Mark
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