[PATCH v1 3/4] gpu: host1x: debug: Fix multiple channels emitting messages simultaneously

Dmitry Osipenko digetx at gmail.com
Sun May 24 17:50:59 UTC 2020

Once channel's job is hung, it dumps the channel's state into KMSG before
tearing down the offending job. If multiple channels hang at once, then
they dump messages simultaneously, making the debug info unreadable, and
thus, useless. This patch adds mutex which allows only one channel to emit
debug messages at a time.

Signed-off-by: Dmitry Osipenko <digetx at gmail.com>
 drivers/gpu/host1x/debug.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/host1x/debug.c b/drivers/gpu/host1x/debug.c
index c0392672a842..1b4997bda1c7 100644
--- a/drivers/gpu/host1x/debug.c
+++ b/drivers/gpu/host1x/debug.c
@@ -16,6 +16,8 @@
 #include "debug.h"
 #include "channel.h"
+static DEFINE_MUTEX(debug_lock);
 unsigned int host1x_debug_trace_cmdbuf;
 static pid_t host1x_debug_force_timeout_pid;
@@ -52,12 +54,14 @@ static int show_channel(struct host1x_channel *ch, void *data, bool show_fifo)
 	struct output *o = data;
+	mutex_lock(&debug_lock);
 	if (show_fifo)
 		host1x_hw_show_channel_fifo(m, ch, o);
 	host1x_hw_show_channel_cdma(m, ch, o);
+	mutex_unlock(&debug_lock);
 	return 0;

More information about the dri-devel mailing list