[PATCH v4 4/7] drm/log: Do not draw if drm_master is taken

[Jocelyn Falempe]

When userspace takes drm_master, the drm_client buffer is no more
visible, so drm_log shouldn't waste CPU cycle to draw on it.

Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_log.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_log.c b/drivers/gpu/drm/drm_log.c
index 376ee173d99d..226e206e8b6a 100644
--- a/drivers/gpu/drm/drm_log.c
+++ b/drivers/gpu/drm/drm_log.c
@@ -18,6 +18,7 @@
 #include <drm/drm_print.h>
 
 #include "drm_draw.h"
+#include "drm_internal.h"
 #include "drm_log.h"
 
 MODULE_AUTHOR("Jocelyn Falempe");
@@ -308,8 +309,13 @@ static void drm_log_write_thread(struct console *con, struct nbcon_write_context
 	if (!dlog->probed)
 		drm_log_init_client(dlog);
 
-	for (i = 0; i < dlog->n_scanout; i++)
-		drm_log_draw_kmsg_record(&dlog->scanout[i], wctxt->outbuf, wctxt->len);
+	/* Check that we are still the master before drawing */
+	if (drm_master_internal_acquire(dlog->client.dev)) {
+		drm_master_internal_release(dlog->client.dev);
+
+		for (i = 0; i < dlog->n_scanout; i++)
+			drm_log_draw_kmsg_record(&dlog->scanout[i], wctxt->outbuf, wctxt->len);
+	}
 }
 
 static void drm_log_lock(struct console *con, unsigned long *flags)
-- 
2.46.2