linux-kernel - [PATCH AUTOSEL 5.2 041/171] drm/crc-debugfs: User irqsafe spinlock in drm_crtc_add_crc

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Message-Id: <20190719035643.14300-41-sashal@kernel.org>
Date:   Thu, 18 Jul 2019 23:54:32 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Emil Velikov <emil.velikov@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.2 041/171] drm/crc-debugfs: User irqsafe spinlock in drm_crtc_add_crc_entry

From: Daniel Vetter <daniel.vetter@...ll.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@...il.com>
Cc: Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc: Emil Velikov <emil.velikov@...labora.com>
Cc: Benjamin Gaignard <benjamin.gaignard@...aro.org>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@...aro.org>
Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190605194556.16744-1-daniel.vetter@ffwll.ch
Signed-off-by: Sasha Levin <sashal@...nel.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