Messages in this thread | | | Date | Tue, 23 Apr 2024 10:47:29 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] lkdtm/bugs: add test for hung smp_call_function_single() |
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On Fri, Apr 19, 2024 at 02:53:59PM -0700, Kees Cook wrote: > On Fri, Apr 19, 2024 at 11:34:52AM +0100, Mark Rutland wrote: > > The CONFIG_CSD_LOCK_WAIT_DEBUG option enables debugging of hung > > smp_call_function*() calls (e.g. when the target CPU gets stuck within > > the callback function). Testing this option requires triggering such > > hangs. > > > > This patch adds an lkdtm test with a hung smp_call_function_single() > > callbac, which can be used to test CONFIG_CSD_LOCK_WAIT_DEBUG and NMI > > backtraces (as CONFIG_CSD_LOCK_WAIT_DEBUG will attempt an NMI backtrace > > of the hung target CPU).
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> > I wrote this because I needed to guide someone through debugging a hung > > smp_call_function() call, and I needed examples with/without an NMI > > backtrace. It seems like it'd be useful for testing the CSD lockup > > detector and NMI backtrace code in future. > > Like the other lockup detector, I suspect we should skip it by default > in the selftests? Something like this: > > diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt > index 368973f05250..32baddc2c85d 100644 > --- a/tools/testing/selftests/lkdtm/tests.txt > +++ b/tools/testing/selftests/lkdtm/tests.txt > @@ -31,6 +31,7 @@ SLAB_FREE_CROSS > SLAB_FREE_PAGE > #SOFTLOCKUP Hangs the system > #HARDLOCKUP Hangs the system > +#CSDLOCKUP Hangs the system > #SPINLOCKUP Hangs the system > #HUNG_TASK Hangs the system > EXEC_DATA
Ah, I wasn't ware of that file, yes.
> > I'm not sure about the CSDLOCKUP name, but everything else I tried > > didn't seem great either: > > > > * IPILOCKUP sounds like it's testing IPIs generally > > * SMPCALLLOCKUP and similar look weirdly long > > * SMP_CALL_LOCKUP and similar look different to {HARD,SOFT,SPIN}LOCKUP > > > > ... and I'm happy to defer to Kees for the naming. ;) > > It looks like it's only useful with CSD lockup detector? If that's true, > sure, this name is fine.
I think it's also useful for testing other things (e.g. RCU stall detection), so how about we go with SMP_CALL_LOCKUP, as that says what the test does rather than what specifically it can be used to test?
Mark.
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