drm/msm/rd: Fix FIFO-full deadlock
authorRob Clark <robdclark@chromium.org>
Sun, 7 Aug 2022 16:09:01 +0000 (09:09 -0700)
committerRob Clark <robdclark@chromium.org>
Sun, 18 Sep 2022 16:37:55 +0000 (09:37 -0700)
If the previous thing cat'ing $debugfs/rd left the FIFO full, then
subsequent open could deadlock in rd_write() (because open is blocked,
not giving a chance for read() to consume any data in the FIFO).  Also
it is generally a good idea to clear out old data from the FIFO.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/496706/
Link: https://lore.kernel.org/r/20220807160901.2353471-2-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>
drivers/gpu/drm/msm/msm_rd.c

index a92ffde..db2f847 100644 (file)
@@ -196,6 +196,9 @@ static int rd_open(struct inode *inode, struct file *file)
        file->private_data = rd;
        rd->open = true;
 
+       /* Reset fifo to clear any previously unread data: */
+       rd->fifo.head = rd->fifo.tail = 0;
+
        /* the parsing tools need to know gpu-id to know which
         * register database to load.
         *