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Thomas Zimmermann 1ff30dd85e drm: Reverse lock order in pan_display_legacy()
Acquiring drm_client_dev.modeset_mutex after the locks in drm_fb_helper.dev
creates a deadlock with drm_setup_crtcs() as shown below:

  [    4.959319] fbcon: radeondrmfb (fb0) is primary device
  [    4.993952] Console: switching to colour frame buffer device 240x67
  [    4.994040]
  [    4.994041] ======================================================
  [    4.994041] WARNING: possible circular locking dependency detected
  [    4.994042] 5.2.0-rc4-1-default+ #39 Tainted: G            E
  [    4.994043] ------------------------------------------------------
  [    4.994043] systemd-udevd/369 is trying to acquire lock:
  [    4.994044] 00000000fb622acb (&client->modeset_mutex){+.+.}, at: drm_fb_helper_pan_display+0x103/0x1f0 [drm_kms_helper]
  [    4.994055]
  [    4.994055] but task is already holding lock:
  [    4.994055] 0000000028767ae4 (crtc_ww_class_mutex){+.+.}, at: drm_modeset_lock+0x42/0xf0 [drm]
  [    4.994072]
  [    4.994072] which lock already depends on the new lock.
  [    4.994072]
  [    4.994072]
  [    4.994072] the existing dependency chain (in reverse order) is:
  [    4.994073]
  [    4.994073] -> #3 (crtc_ww_class_mutex){+.+.}:
  [    4.994076]        lock_acquire+0x9e/0x170
  [    4.994079]        __ww_mutex_lock.constprop.18+0x97/0xf40
  [    4.994080]        ww_mutex_lock+0x30/0x90
  [    4.994091]        drm_modeset_lock+0x42/0xf0 [drm]
  [    4.994102]        drm_modeset_lock_all_ctx+0x1f/0xe0 [drm]
  [    4.994113]        drm_modeset_lock_all+0x5e/0x1a0 [drm]
  [    4.994163]        intel_modeset_init+0x60b/0xda0 [i915]
  ..
  [    4.994253]
  [    4.994253] -> #2 (crtc_ww_class_acquire){+.+.}:
  [    4.994255]        lock_acquire+0x9e/0x170
  [    4.994270]        drm_modeset_acquire_init+0xcc/0x100 [drm]
  [    4.994280]        drm_modeset_lock_all+0x44/0x1a0 [drm]
  [    4.994320]        intel_modeset_init+0x60b/0xda0 [i915]
  ..
  [    4.994403]
  [    4.994403] -> #1 (&dev->mode_config.mutex){+.+.}:
  [    4.994405]        lock_acquire+0x9e/0x170
  [    4.994408]        __mutex_lock+0x62/0x8c0
  [    4.994413]        drm_setup_crtcs+0x17c/0xc50 [drm_kms_helper]
  [    4.994418]        __drm_fb_helper_initial_config_and_unlock+0x34/0x530 [drm_kms_helper]
  [    4.994450]        radeon_fbdev_init+0x110/0x130 [radeon]
  ..
  [    4.994535]
  [    4.994535] -> #0 (&client->modeset_mutex){+.+.}:
  [    4.994537]        __lock_acquire+0xa85/0xe90
  [    4.994538]        lock_acquire+0x9e/0x170
  [    4.994540]        __mutex_lock+0x62/0x8c0
  [    4.994545]        drm_fb_helper_pan_display+0x103/0x1f0 [drm_kms_helper]
  [    4.994547]        fb_pan_display+0x92/0x120
  [    4.994549]        bit_update_start+0x1a/0x40
  [    4.994550]        fbcon_switch+0x392/0x580
  [    4.994552]        redraw_screen+0x12c/0x220
  [    4.994553]        do_bind_con_driver.cold.30+0xe1/0x10d
  [    4.994554]        do_take_over_console+0x113/0x190
  [    4.994555]        do_fbcon_takeover+0x58/0xb0
  [    4.994557]        notifier_call_chain+0x47/0x70
  [    4.994558]        blocking_notifier_call_chain+0x44/0x60
  [    4.994559]        register_framebuffer+0x231/0x310
  [    4.994564]        __drm_fb_helper_initial_config_and_unlock+0x2fd/0x530 [drm_kms_helper]
  [    4.994590]        radeon_fbdev_init+0x110/0x130 [radeon]
  ..

This problem was introduced in

  d81294afe	drm/fb-helper: Remove drm_fb_helper_crtc

Reversing the lock ordering in pan_display_legacy() fixes the issue.

Fixes: d81294afee ("drm/fb-helper: Remove drm_fb_helper_crtc")
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190611115716.7052-1-tzimmermann@suse.de
2019-06-12 10:14:07 +02:00
arch The usual smattering of fixes and tunings that came in too late for the 2019-05-26 13:45:15 -07:00
block blk-mq: fix hang caused by freeze/unfreeze sequence 2019-05-23 10:25:26 -06:00
certs treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
crypto treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 102 2019-05-24 17:39:00 +02:00
Documentation drm/todo: Add bootsplash entry 2019-06-11 14:48:44 +02:00
drivers drm: Reverse lock order in pan_display_legacy() 2019-06-12 10:14:07 +02:00
fs Bug fixes (including a regression fix) for ext4. 2019-05-25 15:03:12 -07:00
include drm/bridge/synopsys: dsi: add power on/off optional phy ops 2019-06-12 09:09:18 +02:00
init treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ipc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 52 2019-05-24 17:36:42 +02:00
kernel Make the GCC 9 warning for sub struct memset go away. 2019-05-26 13:49:40 -07:00
lib for-linus-20190524 2019-05-24 16:02:14 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 98 2019-05-24 17:37:54 +02:00
net SPDX update for 5.2-rc2, round 2 2019-05-24 14:31:58 -07:00
samples treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
scripts Devicetree fixes for 5.2: 2019-05-24 15:16:46 -07:00
security SPDX update for 5.2-rc2, round 2 2019-05-24 14:31:58 -07:00
sound treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 119 2019-05-24 17:39:02 +02:00
tools The usual smattering of fixes and tunings that came in too late for the 2019-05-26 13:45:15 -07:00
usr
virt The usual smattering of fixes and tunings that came in too late for the 2019-05-26 13:45:15 -07:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
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.gitignore .gitignore: exclude .get_maintainer.ignore and .gitattributes 2019-05-18 11:49:54 +09:00
.mailmap A reasonably busy cycle for docs, including: 2019-05-08 12:42:50 -07:00
COPYING
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MAINTAINERS Merge remote-tracking branch 'drm/drm-next' into drm-misc-next 2019-05-28 09:39:08 +02:00
Makefile Linux 5.2-rc2 2019-05-26 16:49:19 -07:00
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