[PATCH] drm/i915/scheduler: Assert that we do not have a dep cycle back to request

[PATCH] drm/i915/scheduler: Assert that we do not have a dep cycle back to request

[Chris Wilson]

When reprioritising a request, we build a list of its dependencies in
topological order. This should leave our origin request as the first
element in our list, if it moves we have a dependency cycle and severe
breakage. Assert that it doesn't move.

Complete, but expensive checking is done by swfence, this assert is more
about documenting the topologically ordered list.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 4e150b095a11..42705e3875cd 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1050,6 +1050,13 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
 		}
 	}
 
+	/*
+	 * We should never have a dep cycle back to ourselves, leaving
+	 * the original request as the origin of our topologically sorted
+	 * list.
+	 */
+	GEM_BUG_ON(list_first_entry(&dfs, typeof(stack), dfs_link) != &stack);
+
 	/*
 	 * If we didn't need to bump any existing priorities, and we haven't
 	 * yet submitted this request (i.e. there is no potential race with
-- 
2.15.1

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✓ Fi.CI.BAT: success for drm/i915/scheduler: Assert that we do not have a dep cycle back to request

[Patchwork]

== Series Details ==

Series: drm/i915/scheduler: Assert that we do not have a dep cycle back to request
URL   : https://patchwork.freedesktop.org/series/36082/
State : success

== Summary ==

Series 36082v1 drm/i915/scheduler: Assert that we do not have a dep cycle back to request
https://patchwork.freedesktop.org/api/1.0/series/36082/revisions/1/mbox/

Test debugfs_test:
        Subgroup read_all_entries:
                dmesg-warn -> PASS       (fi-elk-e7500) fdo#103989 +2
Test kms_pipe_crc_basic:
        Subgroup suspend-read-crc-pipe-b:
                pass       -> DMESG-WARN (fi-kbl-r) fdo#104172 +1

fdo#103989 https://bugs.freedesktop.org/show_bug.cgi?id=103989
fdo#104172 https://bugs.freedesktop.org/show_bug.cgi?id=104172

fi-bdw-5557u     total:288  pass:267  dwarn:0   dfail:0   fail:0   skip:21  time:423s
fi-bdw-gvtdvm    total:288  pass:264  dwarn:0   dfail:0   fail:0   skip:24  time:428s
fi-blb-e6850     total:288  pass:223  dwarn:1   dfail:0   fail:0   skip:64  time:372s
fi-bsw-n3050     total:288  pass:242  dwarn:0   dfail:0   fail:0   skip:46  time:494s
fi-bwr-2160      total:288  pass:183  dwarn:0   dfail:0   fail:0   skip:105 time:277s
fi-bxt-dsi       total:288  pass:258  dwarn:0   dfail:0   fail:0   skip:30  time:482s
fi-bxt-j4205     total:288  pass:259  dwarn:0   dfail:0   fail:0   skip:29  time:483s
fi-byt-j1900     total:288  pass:253  dwarn:0   dfail:0   fail:0   skip:35  time:469s
fi-byt-n2820     total:288  pass:249  dwarn:0   dfail:0   fail:0   skip:39  time:457s
fi-elk-e7500     total:224  pass:168  dwarn:10  dfail:0   fail:0   skip:45 
fi-gdg-551       total:288  pass:179  dwarn:0   dfail:0   fail:1   skip:108 time:264s
fi-glk-1         total:288  pass:260  dwarn:0   dfail:0   fail:0   skip:28  time:511s
fi-hsw-4770      total:288  pass:261  dwarn:0   dfail:0   fail:0   skip:27  time:393s
fi-hsw-4770r     total:288  pass:261  dwarn:0   dfail:0   fail:0   skip:27  time:400s
fi-ilk-650       total:288  pass:228  dwarn:0   dfail:0   fail:0   skip:60  time:413s
fi-ivb-3520m     total:288  pass:259  dwarn:0   dfail:0   fail:0   skip:29  time:449s
fi-ivb-3770      total:288  pass:255  dwarn:0   dfail:0   fail:0   skip:33  time:415s
fi-kbl-7500u     total:288  pass:263  dwarn:1   dfail:0   fail:0   skip:24  time:466s
fi-kbl-7560u     total:288  pass:268  dwarn:1   dfail:0   fail:0   skip:19  time:497s
fi-kbl-7567u     total:288  pass:268  dwarn:0   dfail:0   fail:0   skip:20  time:452s
fi-kbl-r         total:288  pass:260  dwarn:1   dfail:0   fail:0   skip:27  time:503s
fi-pnv-d510      total:288  pass:222  dwarn:1   dfail:0   fail:0   skip:65  time:570s
fi-skl-6260u     total:288  pass:268  dwarn:0   dfail:0   fail:0   skip:20  time:429s
fi-skl-6600u     total:288  pass:260  dwarn:1   dfail:0   fail:0   skip:27  time:505s
fi-skl-6700hq    total:288  pass:261  dwarn:1   dfail:0   fail:0   skip:26  time:529s
fi-skl-6700k2    total:288  pass:264  dwarn:0   dfail:0   fail:0   skip:24  time:496s
fi-skl-6770hq    total:288  pass:268  dwarn:0   dfail:0   fail:0   skip:20  time:473s
fi-skl-gvtdvm    total:288  pass:265  dwarn:0   dfail:0   fail:0   skip:23  time:434s
fi-snb-2520m     total:288  pass:248  dwarn:0   dfail:0   fail:0   skip:40  time:527s
fi-snb-2600      total:288  pass:248  dwarn:0   dfail:0   fail:0   skip:40  time:406s
Blacklisted hosts:
fi-cfl-s2        total:288  pass:262  dwarn:0   dfail:0   fail:0   skip:26  time:569s
fi-cnl-y         total:288  pass:262  dwarn:0   dfail:0   fail:0   skip:26  time:601s
fi-glk-dsi       total:288  pass:258  dwarn:0   dfail:0   fail:0   skip:30  time:468s

914d61a8fb5fc53f6b0366167210468147495b3f drm-tip: 2018y-01m-05d-09h-12m-18s UTC integration manifest
1fc4e0c76021 drm/i915/scheduler: Assert that we do not have a dep cycle back to request

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_7619/issues.html
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✓ Fi.CI.IGT: success for drm/i915/scheduler: Assert that we do not have a dep cycle back to request

[Patchwork]

== Series Details ==

Series: drm/i915/scheduler: Assert that we do not have a dep cycle back to request
URL   : https://patchwork.freedesktop.org/series/36082/
State : success

== Summary ==

Test kms_setmode:
        Subgroup basic:
                pass       -> FAIL       (shard-hsw) fdo#99912
Test kms_flip:
        Subgroup vblank-vs-suspend-interruptible:
                pass       -> INCOMPLETE (shard-hsw) fdo#100368
        Subgroup vblank-vs-modeset-suspend-interruptible:
                skip       -> PASS       (shard-snb)
        Subgroup basic-flip-vs-dpms:
                dmesg-warn -> PASS       (shard-hsw) fdo#102614
Test kms_busy:
        Subgroup extended-modeset-hang-oldfb-with-reset-render-a:
                skip       -> PASS       (shard-snb)
Test kms_frontbuffer_tracking:
        Subgroup fbc-1p-primscrn-spr-indfb-draw-mmap-gtt:
                skip       -> PASS       (shard-snb) fdo#101623 +2
Test gem_tiled_swapping:
        Subgroup non-threaded:
                incomplete -> PASS       (shard-hsw) fdo#104218 +1
Test gem_softpin:
        Subgroup noreloc-s4:
                fail       -> SKIP       (shard-snb) fdo#103375
Test pm_rc6_residency:
        Subgroup rc6-accuracy:
                skip       -> PASS       (shard-snb)
Test kms_cursor_legacy:
        Subgroup cursor-vs-flip-toggle:
                skip       -> PASS       (shard-hsw)

fdo#99912 https://bugs.freedesktop.org/show_bug.cgi?id=99912
fdo#100368 https://bugs.freedesktop.org/show_bug.cgi?id=100368
fdo#102614 https://bugs.freedesktop.org/show_bug.cgi?id=102614
fdo#101623 https://bugs.freedesktop.org/show_bug.cgi?id=101623
fdo#104218 https://bugs.freedesktop.org/show_bug.cgi?id=104218
fdo#103375 https://bugs.freedesktop.org/show_bug.cgi?id=103375

shard-hsw        total:2666 pass:1507 dwarn:1   dfail:0   fail:10  skip:1146 time:8364s
shard-snb        total:2713 pass:1311 dwarn:1   dfail:0   fail:10  skip:1391 time:7874s
Blacklisted hosts:
shard-apl        total:2691 pass:1662 dwarn:1   dfail:0   fail:25  skip:1001 time:12952s
shard-kbl        total:2713 pass:1786 dwarn:16  dfail:2   fail:32  skip:877 time:10537s

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_7619/shards.html
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Re: [PATCH] drm/i915/scheduler: Assert that we do not have a dep cycle back to request

[Michał Winiarski]

On Fri, Jan 05, 2018 at 02:13:22PM +0000, Chris Wilson wrote:
> When reprioritising a request, we build a list of its dependencies in
> topological order. This should leave our origin request as the first
> element in our list, if it moves we have a dependency cycle and severe
> breakage. Assert that it doesn't move.
> 
> Complete, but expensive checking is done by swfence, this assert is more
> about documenting the topologically ordered list.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Michał Winiarski <michal.winiarski@intel.com>

Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>

-Michał

> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 4e150b095a11..42705e3875cd 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -1050,6 +1050,13 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio)
>  		}
>  	}
>  
> +	/*
> +	 * We should never have a dep cycle back to ourselves, leaving
> +	 * the original request as the origin of our topologically sorted
> +	 * list.
> +	 */
> +	GEM_BUG_ON(list_first_entry(&dfs, typeof(stack), dfs_link) != &stack);
> +
>  	/*
>  	 * If we didn't need to bump any existing priorities, and we haven't
>  	 * yet submitted this request (i.e. there is no potential race with
> -- 
> 2.15.1
> 
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