gpu: host1x: debug: Fix multiple channels emitting messages simultaneously

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@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --git a/drivers/gpu/host1x/debug.c b/drivers/gpu/host1x/debug.c
index c0392672a842144b5fe6cc9f2754a8734a16666f..1b4997bda1c799fa3dab94f1168511a4ad38720b 100644 (file)
--- 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(&ch->cdma.lock);
+       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);
        mutex_unlock(&ch->cdma.lock);
 
        return 0;