On Wed, Oct 23, 2024 at 09:38:28PM +0100, Mark Brown wrote: > Currently we test signal delivery to the programs run by fp-stress but > our signal handlers simply count the number of signals seen and don't do > anything with the floating point state. The original fpsimd-test and > sve-test programs had signal handlers called irritators which modify the > live register state, verifying that we restore the signal context on > return, but a combination of misleading comments and code resulted in > them never being used and the equivalent handlers in the other tests > being stubbed or omitted. > > Clarify the code, implement effective irritator handlers for the test > programs that can have them and then switch the signals generated by the > fp-stress program over to use the irritators, ensuring that we validate > that we restore the saved signal context properly. Superficially these look good, but two thing stand out: 1) We only singal the tasks once a second. Dave's original shell test script hammered this constantly, and it makes a substantial impact actually triggering a bug. Without these patches, I hacked the fp-stress.c main loop to trigger a signal every ~1ms (by reducing the epoll_wait() timeout to 1 and scaling the overall timeout to 10000 accordingly), and those changes make the tests reliably trigger the "Bad SVCR" splats within a few seconds after a few hundred signals, even if only using the SIGUSR2 tickle handlers. Can we change the fp-stress.c main loop to signal threads more often? I had some minor changes to only log every ~1000 iterations or so, to avoid spamming the log. 2) The SIGUSR2 tickle handlers are left behind. Given they're unused, it'd be nice to clean them up. Mark. > Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> > --- > Mark Brown (6): > kselftest/arm64: Correct misleading comments on fp-stress irritators > kselftest/arm64: Remove unused ADRs from irritator handlers > kselftest/arm64: Corrupt P15 in the irritator when testing SSVE > kselftest/arm64: Implement irritators for ZA and ZT > kselftest/arm64: Provide a SIGUSR1 handler in the kernel mode FP stress test > kselftest/arm64: Test signal handler state modification in fp-stress > > tools/testing/selftests/arm64/fp/fp-stress.c | 2 +- > tools/testing/selftests/arm64/fp/fpsimd-test.S | 4 +--- > tools/testing/selftests/arm64/fp/kernel-test.c | 4 ++++ > tools/testing/selftests/arm64/fp/sve-test.S | 6 ++---- > tools/testing/selftests/arm64/fp/za-test.S | 13 ++++--------- > tools/testing/selftests/arm64/fp/zt-test.S | 13 ++++--------- > 6 files changed, 16 insertions(+), 26 deletions(-) > --- > base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354 > change-id: 20241023-arm64-fp-stress-irritator-5415fe92adef > > Best regards, > -- > Mark Brown <broonie@xxxxxxxxxx> >
