Re: [Intel-gfx] [PATCH v4 i-g-t 05/15] tests/i915/i915_hangman: Add uevent test & fix detector

[Matthew Brost <matthew.brost@intel.com>]

On Thu, Jan 13, 2022 at 03:51:08PM -0800, John.C.Harrison@Intel.com wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
> 
> Some of the IGT framework relies on receving a uevent when a hang
> occurs. So add a test that this actually works.
> 
> While testing this, noticed that hangs could sometimes be missed
> because the uevent was (presumably) still in flight by the time the
> handler was de-registered. So add an extra delay during cleanup to
> give the uevent chance to arrive.
> 
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  lib/igt_aux.c             |  7 +++++++
>  tests/i915/i915_hangman.c | 43 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/lib/igt_aux.c b/lib/igt_aux.c
> index c247a1aa4..03cc38c93 100644
> --- a/lib/igt_aux.c
> +++ b/lib/igt_aux.c
> @@ -523,6 +523,13 @@ void igt_fork_hang_detector(int fd)
>  
>  void igt_stop_hang_detector(void)
>  {
> +	/*
> +	 * Give the uevent time to arrive. No sleep at all misses about 20% of
> +	 * hangs (at least, in the i915_hangman/detector test). A sleep of 1ms
> +	 * seems to miss about 2%, 10ms loses <1%, so 100ms should be safe.
> +	 */
> +	usleep(100 * 1000);
> +
>  	igt_stop_helper(&hang_detector);
>  }
>  
> diff --git a/tests/i915/i915_hangman.c b/tests/i915/i915_hangman.c
> index 7b8390a6c..354769f39 100644
> --- a/tests/i915/i915_hangman.c
> +++ b/tests/i915/i915_hangman.c
> @@ -31,6 +31,7 @@
>  #include <sys/stat.h>
>  #include <sys/types.h>
>  #include <fcntl.h>
> +#include <signal.h>
>  
>  #include "i915/gem.h"
>  #include "i915/gem_create.h"
> @@ -289,6 +290,38 @@ test_engine_hang(const intel_ctx_t *ctx,
>  	put_ahnd(ahnd);
>  }
>  
> +static int hang_count;
> +
> +static void sig_io(int sig)
> +{
> +	hang_count++;
> +}
> +
> +static void test_hang_detector(const intel_ctx_t *ctx,
> +			       const struct intel_execution_engine2 *e)
> +{
> +	igt_hang_t hang;
> +	uint64_t ahnd = get_reloc_ahnd(device, ctx->id);
> +
> +	hang_count = 0;
> +
> +	igt_fork_hang_detector(device);
> +
> +	/* Steal the signal handler */
> +	signal(SIGIO, sig_io);
> +
> +	/* Make a hang... */
> +	hang = igt_hang_ctx_with_ahnd(device, ahnd, ctx->id, e->flags, 0);
> +
> +	igt_post_hang_ring(device, hang);
> +	put_ahnd(ahnd);
> +
> +	igt_stop_hang_detector();
> +
> +	/* Did it work? */
> +	igt_assert(hang_count == 1);
> +}
> +
>  /* This test covers the case where we end up in an uninitialised area of the
>   * ppgtt and keep executing through it. This is particularly relevant if 48b
>   * ppgtt is enabled because the ppgtt is massively bigger compared to the 32b
> @@ -408,6 +441,16 @@ igt_main
>  	igt_subtest("hangcheck-unterminated")
>  		hangcheck_unterminated(ctx);
>  
> +	igt_describe("Check that hang detector works");
> +	igt_subtest_with_dynamic("detector") {
> +		const struct intel_execution_engine2 *e;
> +
> +		for_each_ctx_engine(device, ctx, e) {
> +			igt_dynamic_f("%s", e->name)
> +				test_hang_detector(ctx, e);
> +		}
> +	}
> +
>  	do_tests("GT", "gt", ctx);
>  
>  	igt_fixture {
> -- 
> 2.25.1
>