[PATCH] drm/i915: Replace irq_seqno_barrier on hws write with a clflush

[PATCH] drm/i915: Replace irq_seqno_barrier on hws write with a clflush

[Chris Wilson]

When manually overwriting the HWS, rather than assume irq_seqno_barrier
does the right thing, we can explicitly flush the cacheline instead.
This avoids us calling the engine->irq_seqno_barrier() from an illegal
context:

[ 1472.651797] BUG: scheduling while atomic: migration/0/11/0x00000002
[ 1472.651807] Modules linked in: ctr ccm arc4 snd_hda_codec_hdmi bnep rfcomm iwldvm snd_hda_codec_conexant snd_hda_codec_generic snd_hda_intel mac80211 snd_hda_codec snd_hda_core snd_pcm dm_multipath snd_hwdep intel_powerclamp coretemp snd_seq_midi crct10dif_pclmul snd_seq_midi_event crc32_pclmul iwlwifi ghash_clmulni_intel btusb snd_rawmidi btrtl aesni_intel btbcm aes_x86_64 crypto_simd btintel cryptd glue_helper bluetooth snd_seq cfg80211 snd_timer snd_seq_device intel_ips binfmt_misc snd mei_me soundcore mei dm_mirror dm_region_hash dm_log i915 intel_gtt i2c_algo_bit drm_kms_helper cfbfillrect syscopyarea cfbimgblt sysfillrect sysimgblt fb_sys_fops cfbcopyarea prime_numbers e1000e drm ahci libahci
[ 1472.651897] CPU: 0 PID: 11 Comm: migration/0 Tainted: G     U          4.11.0-rc1+ #203
[ 1472.651899] Hardware name: LENOVO 514328U/514328U, BIOS 6QET44WW (1.14 ) 04/20/2010
[ 1472.651900] Call Trace:
[ 1472.651913]  dump_stack+0x63/0x90
[ 1472.651922]  __schedule_bug+0x5d/0x6b
[ 1472.651930]  __schedule+0x46a/0x5f0
[ 1472.651934]  schedule+0x38/0x90
[ 1472.651938]  schedule_hrtimeout_range_clock+0x85/0x110
[ 1472.651945]  ? hrtimer_init+0x10/0x10
[ 1472.651949]  schedule_hrtimeout_range+0xe/0x10
[ 1472.651952]  usleep_range+0x4d/0x60
[ 1472.652037]  gen5_seqno_barrier+0x13/0x20 [i915]
[ 1472.652101]  intel_engine_init_global_seqno+0xd7/0x160 [i915]
[ 1472.652160]  __i915_gem_set_wedged_BKL+0xa0/0x180 [i915]
[ 1472.652166]  multi_cpu_stop+0xbb/0xe0
[ 1472.652170]  ? cpu_stop_queue_work+0x90/0x90
[ 1472.652174]  cpu_stopper_thread+0x82/0x110
[ 1472.652179]  smpboot_thread_fn+0x137/0x190
[ 1472.652184]  kthread+0xf7/0x130
[ 1472.652187]  ? sort_range+0x20/0x20
[ 1472.652191]  ? kthread_park+0x90/0x90
[ 1472.652195]  ret_from_fork+0x2c/0x40

Testcase: igt/gem_eio #ilk
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_engine_cs.c  | 3 +--
 drivers/gpu/drm/i915/intel_ringbuffer.h | 4 ++++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 5663ebab851f..074ecaae6daa 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -249,8 +249,7 @@ void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno)
 	}
 
 	intel_write_status_page(engine, I915_GEM_HWS_INDEX, seqno);
-	if (engine->irq_seqno_barrier)
-		engine->irq_seqno_barrier(engine);
+	clear_bit(ENGINE_IRQ_BREADCRUMB, &engine->irq_posted);
 
 	GEM_BUG_ON(i915_gem_active_isset(&engine->timeline->last_request));
 	engine->hangcheck.seqno = seqno;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 9011ae484bd5..bad5e455e815 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -468,7 +468,11 @@ static inline void
 intel_write_status_page(struct intel_engine_cs *engine,
 			int reg, u32 value)
 {
+	mb();
+	clflush(&engine->status_page.page_addr[reg]);
 	engine->status_page.page_addr[reg] = value;
+	clflush(&engine->status_page.page_addr[reg]);
+	mb();
 }
 
 /*
-- 
2.11.0

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Re: [PATCH] drm/i915: Replace irq_seqno_barrier on hws write with a clflush

[Chris Wilson]

On Tue, Mar 14, 2017 at 11:38:59AM +0000, Chris Wilson wrote:
> When manually overwriting the HWS, rather than assume irq_seqno_barrier
> does the right thing, we can explicitly flush the cacheline instead.
> This avoids us calling the engine->irq_seqno_barrier() from an illegal
> context:

Drat, this was meant to be the other patch that I missent!
Sorry for the noise
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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✗ Fi.CI.BAT: failure for drm/i915: Replace irq_seqno_barrier on hws write with a clflush (rev2)

[Patchwork]

== Series Details ==

Series: drm/i915: Replace irq_seqno_barrier on hws write with a clflush (rev2)
URL   : https://patchwork.freedesktop.org/series/21210/
State : failure

== Summary ==

Series 21210v2 drm/i915: Replace irq_seqno_barrier on hws write with a clflush
https://patchwork.freedesktop.org/api/1.0/series/21210/revisions/2/mbox/

Test gem_exec_reloc:
        Subgroup basic-write-gtt-active:
                pass       -> INCOMPLETE (fi-byt-j1900)
Test kms_cursor_legacy:
        Subgroup basic-busy-flip-before-cursor-atomic:
                fail       -> PASS       (fi-snb-2520m)

fi-bdw-5557u     total:278  pass:267  dwarn:0   dfail:0   fail:0   skip:11  time: 479s
fi-bsw-n3050     total:278  pass:239  dwarn:0   dfail:0   fail:0   skip:39  time: 585s
fi-bxt-j4205     total:278  pass:259  dwarn:0   dfail:0   fail:0   skip:19  time: 533s
fi-bxt-t5700     total:278  pass:258  dwarn:0   dfail:0   fail:0   skip:20  time: 550s
fi-byt-j1900     total:96   pass:86   dwarn:0   dfail:0   fail:0   skip:9   time: 0s
fi-byt-n2820     total:278  pass:247  dwarn:0   dfail:0   fail:0   skip:31  time: 499s
fi-hsw-4770      total:278  pass:262  dwarn:0   dfail:0   fail:0   skip:16  time: 440s
fi-hsw-4770r     total:278  pass:262  dwarn:0   dfail:0   fail:0   skip:16  time: 435s
fi-ilk-650       total:278  pass:228  dwarn:0   dfail:0   fail:0   skip:50  time: 435s
fi-ivb-3520m     total:278  pass:260  dwarn:0   dfail:0   fail:0   skip:18  time: 510s
fi-ivb-3770      total:278  pass:260  dwarn:0   dfail:0   fail:0   skip:18  time: 492s
fi-kbl-7500u     total:278  pass:260  dwarn:0   dfail:0   fail:0   skip:18  time: 479s
fi-skl-6260u     total:278  pass:268  dwarn:0   dfail:0   fail:0   skip:10  time: 483s
fi-skl-6700hq    total:278  pass:261  dwarn:0   dfail:0   fail:0   skip:17  time: 597s
fi-skl-6700k     total:278  pass:256  dwarn:4   dfail:0   fail:0   skip:18  time: 489s
fi-skl-6770hq    total:278  pass:268  dwarn:0   dfail:0   fail:0   skip:10  time: 528s
fi-snb-2520m     total:278  pass:250  dwarn:0   dfail:0   fail:0   skip:28  time: 549s
fi-snb-2600      total:278  pass:249  dwarn:0   dfail:0   fail:0   skip:29  time: 419s

c641417b70c6b78efca29ae732d7cbf5716ac6d5 drm-tip: 2017y-03m-14d-16h-04m-56s UTC integration manifest
10cde01 drm/i915: Replace irq_seqno_barrier on hws write with a clflush

== Logs ==

For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_4161/
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