From: Hugh Dickins hughd@chromium.org Subject: drm: avoid switching to text console if there is no panic timeout

Add a check for panic_timeout in the drm_fb_helper_panic() notifier: if we're going to reboot immediately, the user will not be able to see the messages anyway, and messing with the video mode may display artifacts, and certainly get into several layers of complexity (including mutexes and memory allocations) which we shall be much safer to avoid.

[msb@chromium.org: edited commit message and modified to short-circuit panic_timeout < 0 instead of testing panic_timeout >= 0] Signed-off-by: Hugh Dickins hughd@google.com Signed-off-by: Mandeep Singh Baines msb@chromium.org Cc: Dave Airlie airlied@redhat.com Acked-by: David Rientjes rientjes@google.com Acked-by: Stéphane Marchesin marcheu@chromium.org Cc: Dave Young hidave.darkstar@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

drivers/gpu/drm/drm_fb_helper.c | 7 +++++++ 1 file changed, 7 insertions(+)

diff -puN drivers/gpu/drm/drm_fb_helper.c~drm-avoid-switching-to-text-console-if-there-is-no-panic-timeout drivers/gpu/drm/drm_fb_helper.c --- a/drivers/gpu/drm/drm_fb_helper.c~drm-avoid-switching-to-text-console-if-there-is-no-panic-timeout +++ a/drivers/gpu/drm/drm_fb_helper.c @@ -255,6 +255,13 @@ bool drm_fb_helper_force_kernel_mode(voi int drm_fb_helper_panic(struct notifier_block *n, unsigned long ununsed, void *panic_str) { + /* + * It's a waste of time and effort to switch back to text console + * if the kernel should reboot before panic messages can be seen. + */ + if (panic_timeout < 0) + return 0; + printk(KERN_ERR "panic occurred, switching back to text console\n"); return drm_fb_helper_force_kernel_mode(); } _