drm/log: Do not draw if drm_master is taken

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@redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20241204160014.1171469-4-jfalempe@redhat.com

diff --git a/drivers/gpu/drm/clients/drm_log.c b/drivers/gpu/drm/clients/drm_log.c
index 4e07bff6c8646bf2e57bf130a427128766e515fa..a933da024b1ae2e727ce5b0adc9f6ac5bd292031 100644 (file)
--- a/drivers/gpu/drm/clients/drm_log.c
+++ b/drivers/gpu/drm/clients/drm_log.c
@@ -19,6 +19,7 @@
 
 #include "drm_client_internal.h"
 #include "drm_draw_internal.h"
+#include "drm_internal.h"
 
 MODULE_AUTHOR("Jocelyn Falempe");
 MODULE_DESCRIPTION("DRM boot logger");
@@ -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)