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From: Gerd Hoffmann <kraxel@redhat.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Jaak Ristioja <jaak@ristioja.ee>,
	Dave Airlie <airlied@redhat.com>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	virtualization@lists.linux-foundation.org,
	spice-devel@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: Xorg indefinitely hangs in kernelspace
Date: Mon, 9 Sep 2019 07:52:19 +0200	[thread overview]
Message-ID: <20190909055219.q44k27cczwkuio3z@sirius.home.kraxel.org> (raw)
In-Reply-To: <20190906055322.17900-1-hdanton@sina.com>

  Hi,

--verbose please.  Do you see the same hang?  Does the patch fix it?

> --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> @@ -97,8 +97,9 @@ int ttm_eu_reserve_buffers(struct ww_acq
>  			   struct list_head *dups, bool del_lru)
[ ... ]

> +			if (locked)
> +				ttm_eu_backoff_reservation_reverse(list, entry);

Hmm, I think the patch is wrong.  As far I know it is the qxl drivers's
job to call ttm_eu_backoff_reservation().  Doing that automatically in
ttm will most likely break other ttm users.

So I guess the call is missing in the qxl driver somewhere, most likely
in some error handling code path given that this bug is a relatively
rare event.

There is only a single ttm_eu_reserve_buffers() call in qxl.
So how about this?

----------------------- cut here --------------------
diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c
index 312216caeea2..2f9950fa0b8d 100644
--- a/drivers/gpu/drm/qxl/qxl_release.c
+++ b/drivers/gpu/drm/qxl/qxl_release.c
@@ -262,18 +262,20 @@ int qxl_release_reserve_list(struct qxl_release *release, bool no_intr)
 	ret = ttm_eu_reserve_buffers(&release->ticket, &release->bos,
 				     !no_intr, NULL, true);
 	if (ret)
-		return ret;
+		goto err_backoff;
 
 	list_for_each_entry(entry, &release->bos, tv.head) {
 		struct qxl_bo *bo = to_qxl_bo(entry->tv.bo);
 
 		ret = qxl_release_validate_bo(bo);
-		if (ret) {
-			ttm_eu_backoff_reservation(&release->ticket, &release->bos);
-			return ret;
-		}
+		if (ret)
+			goto err_backoff;
 	}
 	return 0;
+
+err_backoff:
+	ttm_eu_backoff_reservation(&release->ticket, &release->bos);
+	return ret;
 }
 
 void qxl_release_backoff_reserve_list(struct qxl_release *release)
----------------------- cut here --------------------

cheers,
  Gerd


WARNING: multiple messages have this Message-ID (diff)
From: Gerd Hoffmann <kraxel@redhat.com>
To: Hillf Danton <hdanton@sina.com>
Cc: David Airlie <airlied@linux.ie>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	virtualization@lists.linux-foundation.org,
	Daniel Vetter <daniel@ffwll.ch>,
	spice-devel@lists.freedesktop.org,
	Jaak Ristioja <jaak@ristioja.ee>,
	Dave Airlie <airlied@redhat.com>
Subject: Re: Xorg indefinitely hangs in kernelspace
Date: Mon, 9 Sep 2019 07:52:19 +0200	[thread overview]
Message-ID: <20190909055219.q44k27cczwkuio3z@sirius.home.kraxel.org> (raw)
In-Reply-To: <20190906055322.17900-1-hdanton@sina.com>

  Hi,

--verbose please.  Do you see the same hang?  Does the patch fix it?

> --- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
> @@ -97,8 +97,9 @@ int ttm_eu_reserve_buffers(struct ww_acq
>  			   struct list_head *dups, bool del_lru)
[ ... ]

> +			if (locked)
> +				ttm_eu_backoff_reservation_reverse(list, entry);

Hmm, I think the patch is wrong.  As far I know it is the qxl drivers's
job to call ttm_eu_backoff_reservation().  Doing that automatically in
ttm will most likely break other ttm users.

So I guess the call is missing in the qxl driver somewhere, most likely
in some error handling code path given that this bug is a relatively
rare event.

There is only a single ttm_eu_reserve_buffers() call in qxl.
So how about this?

----------------------- cut here --------------------
diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c
index 312216caeea2..2f9950fa0b8d 100644
--- a/drivers/gpu/drm/qxl/qxl_release.c
+++ b/drivers/gpu/drm/qxl/qxl_release.c
@@ -262,18 +262,20 @@ int qxl_release_reserve_list(struct qxl_release *release, bool no_intr)
 	ret = ttm_eu_reserve_buffers(&release->ticket, &release->bos,
 				     !no_intr, NULL, true);
 	if (ret)
-		return ret;
+		goto err_backoff;
 
 	list_for_each_entry(entry, &release->bos, tv.head) {
 		struct qxl_bo *bo = to_qxl_bo(entry->tv.bo);
 
 		ret = qxl_release_validate_bo(bo);
-		if (ret) {
-			ttm_eu_backoff_reservation(&release->ticket, &release->bos);
-			return ret;
-		}
+		if (ret)
+			goto err_backoff;
 	}
 	return 0;
+
+err_backoff:
+	ttm_eu_backoff_reservation(&release->ticket, &release->bos);
+	return ret;
 }
 
 void qxl_release_backoff_reserve_list(struct qxl_release *release)
----------------------- cut here --------------------

cheers,
  Gerd

  parent reply	other threads:[~2019-09-09  5:53 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-06  5:53 Xorg indefinitely hangs in kernelspace Hillf Danton
2019-09-06 20:27 ` [Spice-devel] " Frediano Ziglio
2019-09-06 20:27   ` Frediano Ziglio
2019-09-07  2:00   ` Hillf Danton
2019-09-07  2:00     ` Hillf Danton
2019-09-07  2:00   ` Hillf Danton
2019-09-07  2:00   ` [Spice-devel] " Hillf Danton
2019-09-09  5:52 ` Gerd Hoffmann [this message]
2019-09-09  5:52   ` Gerd Hoffmann
2019-09-09  7:13   ` Hillf Danton
2019-09-09  7:13   ` Hillf Danton
2019-09-09  7:13   ` Hillf Danton
  -- strict thread matches above, loose matches on Subject: below --
2019-09-09 12:12 Hillf Danton
2019-08-06 18:00 Jaak Ristioja
2019-09-05  7:14 ` Gerd Hoffmann
2019-09-05  7:14   ` Gerd Hoffmann
2019-09-05 12:34   ` Jaak Ristioja
2019-09-05 12:34   ` Jaak Ristioja
2019-09-24  9:12     ` Jaak Ristioja
2019-09-24  9:12     ` Jaak Ristioja
2019-09-05  7:14 ` Gerd Hoffmann

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