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

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> 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 at chris-wilson.co.uk>

Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>

> ---
>  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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