[igt-dev] [PATCH i-g-t] tests/i915_suspend: Free device list after *-without-i915 subtests

[Janusz Krzysztofik]

On Thursday, 9 February 2023 20:32:31 CET Janusz Krzysztofik wrote:
> If any of *-without-i915 subtests fails or skips for any reason, it may
> leave the i915 module unloaded while keeping our device list populated
> with initially collected data.  In a follow up igt_fixture section we then
> try to reopen the device.  If the test has been executed with a device
> filter specified, an attempt to open the device finds a matching entry
> that belongs to the no longer existing device in that initially collected
> device list, fails to stat() it, concludes that's because of the device
> having been already open, and returns an error.
> 
> Fix this potentially confusing test result by freeing the potentially
> outdated device list before continuing with drm_open_driver().

Freeing device list occurred not safe if device scan was not performed before.  
I can see 3 potential solutions:
1) force device rescan instead of free before calling drm_open_driver(),
2) teach igt_device_free() to return immediately if the device list has not 
   been allocated,
3) provide a has_device_list() helper for to be used if not sure before 
   calling igt_device_free().

Any preferences?

Thanks,
Janusz

> 
> While being at it, add a comment that explains why we call
> igt_device_scan() from __igt_device_card_match() but don't force device
> rescan, and emit a debug message if we fail in _is_already_opened() on
> unsuccessful device stat().
> 
> Subtest basic-s3-without-i915: FAIL (9.572s)
> (i915_suspend:9050) drmtest-WARNING: card maching filter 0 is already opened
> (i915_suspend:9050) drmtest-CRITICAL: Test abort in function drm_open_driver, file ../lib/drmtest.c:639:
> (i915_suspend:9050) drmtest-CRITICAL: abort condition: fd < 0
> (i915_suspend:9050) drmtest-CRITICAL: Last errno: 2, No such file or directory
> (i915_suspend:9050) drmtest-CRITICAL: No known gpu found for chipset flags 0x1 (intel)
> Test i915_suspend failed.
> **** DEBUG ****
> (i915_suspend:9050) drmtest-DEBUG: Looking for devices to open using filter 0: pci:vendor=intel,device=dg2
> (i915_suspend:9050) drmtest-DEBUG: Filter matched /dev/dri/card0 | /dev/dri/renderD128
> (i915_suspend:9050) drmtest-WARNING: card maching filter 0 is already opened
> (i915_suspend:9050) drmtest-CRITICAL: Test abort in function drm_open_driver, file ../lib/drmtest.c:639:
> (i915_suspend:9050) drmtest-CRITICAL: abort condition: fd < 0
> (i915_suspend:9050) drmtest-CRITICAL: Last errno: 2, No such file or directory
> (i915_suspend:9050) drmtest-CRITICAL: No known gpu found for chipset flags 0x1 (intel)
> (i915_suspend:9050) igt_core-INFO: Stack trace:
> (i915_suspend:9050) igt_core-INFO:   #0 ../lib/igt_core.c:2066 __igt_abort()
> (i915_suspend:9050) igt_core-INFO:   #1 ../lib/drmtest.c:573 drm_open_driver()
> (i915_suspend:9050) igt_core-INFO:   #2 ../tests/i915/i915_suspend.c:258 __igt_unique____real_main245()
> (i915_suspend:9050) igt_core-INFO:   #3 ../tests/i915/i915_suspend.c:245 main()
> (i915_suspend:9050) igt_core-INFO:   #4 ../sysdeps/nptl/libc_start_call_main.h:58 __libc_start_call_main()
> (i915_suspend:9050) igt_core-INFO:   #5 ../csu/libc-start.c:128 __libc_start_main@@GLIBC_2.34()
> (i915_suspend:9050) igt_core-INFO:   #6 [_start+0x2a]
> ****  END  ****
> 
> Fixes: f7aff600ab16 ("tests/i915/i915_suspend: Disable d3cold_allowed for basic-s2idle-without-i915")
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: Riana Tauro <riana.tauro at intel.com>
> ---
>  lib/drmtest.c             |  2 +-
>  lib/igt_device_scan.c     |  4 ++++
>  tests/i915/i915_suspend.c | 10 +++++++++-
>  3 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/drmtest.c b/lib/drmtest.c
> index 16e80bdfcf..8e2d1ac50b 100644
> --- a/lib/drmtest.c
> +++ b/lib/drmtest.c
> @@ -260,7 +260,7 @@ static bool _is_already_opened(const char *path, int as_idx)
>  	 * we cannot even stat the device, so it's of no use - let's claim it's
>  	 * already opened
>  	 */
> -	if (stat(path, &new) != 0)
> +	if (igt_debug_on(stat(path, &new) != 0))
>  		return true;
>  
>  	for (int i = 0; i < as_idx; ++i) {
> diff --git a/lib/igt_device_scan.c b/lib/igt_device_scan.c
> index 8b767eed20..ae69ed09f1 100644
> --- a/lib/igt_device_scan.c
> +++ b/lib/igt_device_scan.c
> @@ -1918,6 +1918,10 @@ static bool __igt_device_card_match(const char *filter,
>  		return false;
>  	memset(card, 0, sizeof(*card));
>  
> +	/*
> +	 * Scan devices in case the user hasn't yet,
> +	 * but leave a decision on forced rescan on the user side.
> +	 */
>  	igt_devices_scan(false);
>  
>  	if (igt_device_filter_apply(filter) == false)
> diff --git a/tests/i915/i915_suspend.c b/tests/i915/i915_suspend.c
> index 815f1c8a2c..c68110476e 100644
> --- a/tests/i915/i915_suspend.c
> +++ b/tests/i915/i915_suspend.c
> @@ -253,8 +253,16 @@ igt_main
>  	igt_subtest("basic-s3-without-i915")
>  		test_suspend_without_i915(SUSPEND_STATE_S3);
>  
> -	igt_fixture
> +	igt_fixture {
> +		/*
> +		 * Since above tests may fail leaving the i915 module unloaded,
> +		 * force refresh of device list before opening an i915 device
> +		 * by cleaning up the current device list, otherwise we can fail
> +		 * if we have been called with a device filter specified.
> +		 */
> +		igt_devices_free();
>  		fd = drm_open_driver(DRIVER_INTEL);
> +	}
>  
>  	igt_subtest("fence-restore-tiled2untiled") {
>  		gem_require_mappable_ggtt(fd);
>