On 08/11/2024 14:33, Thomas Zimmermann wrote:
Hi
Am 08.11.24 um 09:10 schrieb 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 376ee173d99d9..226e206e8b6a3 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)) {
Just a note: it would be better to track this state in the client code
and handle these locks automatically. But it's ok for now. It would
require an overhaul of the fbdev helpers as well.
+ drm_master_internal_release(dlog->client.dev);
Don't you have to release after drawing?
I'm not sure, the drawing code will only call
drm_client_buffer_vmap_local() / unmap
and drm_client_framebuffer_flush(), and they don't require the master
lock to be taken. I think master lock is needed only for modesetting.
Also the dlog->lock is taken by the console thread, so there are no race
conditions with the drm_client callbacks (hotplug/suspend/resume).
Best regards
Thomas
+
+ 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)
