[PATCH AUTOSEL 5.1 031/141] drm/crc-debugfs: User irqsafe spinlock in drm_crtc_add_crc_entry

Sasha Levin
2019-07-19T04:03:58Z

From: Daniel Vetter <daniel.vetter@ffwll.ch>

[ Upstream commit 1882018a70e06376234133e69ede9dd743b4dbd9 ]

We can be called from any context, we need to be prepared.

Noticed this while hacking on vkms, which calls this function from a
normal worker. Which really upsets lockdep.

Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190605194556.16744-1-daniel.vetter@ffwll.ch
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/drm_debugfs_crc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c
index 00e743153e94..1a6a5b78e30f 100644
--- a/drivers/gpu/drm/drm_debugfs_crc.c
+++ b/drivers/gpu/drm/drm_debugfs_crc.c
@@ -389,8 +389,9 @@ int drm_crtc_add_crc_entry(struct drm_crtc *crtc, bool has_frame,
struct drm_crtc_crc *crc = &crtc->crc;
struct drm_crtc_crc_entry *entry;
int head, tail;
+ unsigned long flags;

- spin_lock(&crc->lock);
+ spin_lock_irqsave(&crc->lock, flags);

/* Caller may not have noticed yet that userspace has stopped reading */
if (!crc->entries) {
@@ -421,7 +422,7 @@ int drm_crtc_add_crc_entry(struct drm_crtc *crtc, bool has_frame,
head = (head + 1) & (DRM_CRC_ENTRIES_NR - 1);
crc->head = head;

- spin_unlock(&crc->lock);
+ spin_unlock_irqrestore(&crc->lock, flags);

wake_up_interruptible(&crc->wq);

--
2.20.1