[PATCH 4.6 135/203] drm/atomic: Make drm_atomic_legacy_backoff reset crtc->acquire_ctx

Greg Kroah-Hartman
2016-07-25T22:07:21Z

From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

commit 81e257e964268d050f8e9188becd44d50f241d72 upstream.

Atomic updates may acquire more state than initially locked through
drm_modeset_lock_crtc, running with heavy stress can cause a
WARN_ON(crtc->acquire_ctx) in drm_modeset_lock_crtc:

[ 601.491296] ------------[ cut here ]------------
[ 601.491366] WARNING: CPU: 0 PID: 2411 at
drivers/gpu/drm/drm_modeset_lock.c:191 drm_modeset_lock_crtc+0xeb/0xf0 [drm]
[ 601.491369] Modules linked in: drm i915 drm_kms_helper
[ 601.491414] CPU: 0 PID: 2411 Comm: kms_cursor_lega Tainted: G U 4.7.0-rc4-patser+ #4798
[ 601.491417] Hardware name: Intel Corporation Skylake Client
[ 601.491420] 0000000000000000 ffff88044d153c98 ffffffff812ead28 0000000000000000
[ 601.491425] 0000000000000000 ffff88044d153cd8 ffffffff810868e6 000000bf58058030
[ 601.491431] ffff880088b415e8 ffff880458058030 ffff88008a271548 ffff88008a271568
[ 601.491436] Call Trace:
[ 601.491443] [<ffffffff812ead28>] dump_stack+0x4d/0x65
[ 601.491447] [<ffffffff810868e6>] __warn+0xc6/0xe0
[ 601.491452] [<ffffffff81086968>] warn_slowpath_null+0x18/0x20
[ 601.491472] [<ffffffffc00d4ffb>] drm_modeset_lock_crtc+0xeb/0xf0 [drm]
[ 601.491491] [<ffffffffc00c5526>] drm_mode_cursor_common+0x66/0x180 [drm]
[ 601.491509] [<ffffffffc00c91cc>] drm_mode_cursor_ioctl+0x3c/0x40 [drm]
[ 601.491524] [<ffffffffc00bc94d>] drm_ioctl+0x14d/0x530 [drm]
[ 601.491540] [<ffffffffc00c9190>] ? drm_mode_setcrtc+0x520/0x520 [drm]
[ 601.491545] [<ffffffff81176aeb>] ? handle_mm_fault+0x106b/0x1430
[ 601.491550] [<ffffffff81108441>] ? stop_one_cpu+0x61/0x70
[ 601.491556] [<ffffffff811bb71d>] do_vfs_ioctl+0x8d/0x570
[ 601.491560] [<ffffffff81290d7e>] ? security_file_ioctl+0x3e/0x60
[ 601.491565] [<ffffffff811bbc74>] SyS_ioctl+0x74/0x80
[ 601.491571] [<ffffffff810e321c>] ? posix_get_monotonic_raw+0xc/0x10
[ 601.491576] [<ffffffff8175b11b>] entry_SYSCALL_64_fastpath+0x13/0x8f
[ 601.491581] ---[ end trace 56f3d3d85f000d00 ]---

For good measure, test mode_config.acquire_ctx too, although this should
never happen.

Testcase: kms_cursor_legacy
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/drm_atomic.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1288,14 +1288,39 @@ EXPORT_SYMBOL(drm_atomic_add_affected_pl
*/
void drm_atomic_legacy_backoff(struct drm_atomic_state *state)
{
+ struct drm_device *dev = state->dev;
+ unsigned crtc_mask = 0;
+ struct drm_crtc *crtc;
int ret;
+ bool global = false;
+
+ drm_for_each_crtc(crtc, dev) {
+ if (crtc->acquire_ctx != state->acquire_ctx)
+ continue;
+
+ crtc_mask |= drm_crtc_mask(crtc);
+ crtc->acquire_ctx = NULL;
+ }
+
+ if (WARN_ON(dev->mode_config.acquire_ctx == state->acquire_ctx)) {
+ global = true;
+
+ dev->mode_config.acquire_ctx = NULL;
+ }

retry:
drm_modeset_backoff(state->acquire_ctx);

- ret = drm_modeset_lock_all_ctx(state->dev, state->acquire_ctx);
+ ret = drm_modeset_lock_all_ctx(dev, state->acquire_ctx);
if (ret)
goto retry;
+
+ drm_for_each_crtc(crtc, dev)
+ if (drm_crtc_mask(crtc) & crtc_mask)
+ crtc->acquire_ctx = state->acquire_ctx;
+
+ if (global)
+ dev->mode_config.acquire_ctx = state->acquire_ctx;
}
EXPORT_SYMBOL(drm_atomic_legacy_backoff);