drm/crc-debugfs: User irqsafe spinlock in drm_crtc_add_crc_entry

BugLink: https://bugs.launchpad.net/bugs/1839036
[ 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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c
index 9dd879589a2c56d701f4604dadff0040851b854e..acf86944fcd79fe0cb5b3a114efcba52bfddd438 100644 (file)
--- a/drivers/gpu/drm/drm_debugfs_crc.c
+++ b/drivers/gpu/drm/drm_debugfs_crc.c
@@ -359,8 +359,9 @@ 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) {
@@ -385,7 +386,7 @@ 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);