On Tue, Jun 22, 2010 at 8:12 PM, Dave Airlie [off-list ref] wrote:
From: Jesse Barnes <redacted>
Jesse's initial patch commit said:
"At panic time (i.e. when oops_in_progress is set) we should try a bit
harder to update the screen and make sure output gets to the VT, since
some drivers are capable of flipping back to it.
So make sure we try to unblank and update the display if called from a
panic context."
I've enhanced this to add a flag to the vc that console layer can set
to indicate they want this behaviour to occur. This also adds support
to fbcon for that flag and adds an fb flag for drivers to indicate
they want to use the support. It enables this for KMS drivers.
Signed-off-by: Dave Airlie <airlied@redhat.com>
Hi Dave,
I think this change is causing a regression I'm seeing in panic.
Before this change, I'd get a
reboot on panic (we've configured as such).
With this change, my machine gets wedged if the machine is running in
X when the panic occurs.
I traced the code flow to this:
bust_spinlocks(0);
->unblank_screen();
->do_unblank_screen(0);
->vc->vc_sw->con_blank(vc, 0, 0);
->fbcon_blank(vc, 0, 0);
->update_screen(vc);
->redraw_screen(vc, 0);
->vc->vc_sw->con_switch(vc);
->fbcon_switch(vc);
->ops->update_start(info);
->bit_update_start(info);
->fb_pan_display(info, &ops->var);
->info->fbops->fb_pan_display(var, info);
->drm_fb_helper_pan_display(var, info);
->mutex_lock(&dev->mode_config.mutex); *this blocks*
With this change, there is now a lot going on in the panic path. Stuff
that I'm not sure is safe when panicking. In addition to the
mutex_lock, there is also a del_timer_sync()
now happening in the context of panic().
I see this bug with a 2.6.38 kernel but did a quick scan of a newer
kernels and did not see anything that changed in this path so I
suspect its still there.
Reverting this change fixes the regression.
Regards,2 more lines
quoted hunk
---
drivers/char/vt.c | 13 +++++++++----
drivers/gpu/drm/i915/intel_fb.c | 4 +---
drivers/gpu/drm/nouveau/nouveau_fbcon.c | 1 +
drivers/gpu/drm/radeon/radeon_fb.c | 2 +-
drivers/video/console/fbcon.c | 4 +++-
include/linux/console_struct.h | 1 +
include/linux/fb.h | 4 ++++
include/linux/vt_kern.h | 7 +++++++
8 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 7cdb6ee..6e04c9e 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -698,7 +698,10 @@ void redraw_screen(struct vc_data *vc, int is_switch)
update_attr(vc);
clear_buffer_attributes(vc);
}
- if (update && vc->vc_mode != KD_GRAPHICS)
+
+ /* Forcibly update if we're panicing */
+ if ((update && vc->vc_mode != KD_GRAPHICS) ||
+ vt_force_oops_output(vc))
do_update_region(vc, vc->vc_origin, vc->vc_screenbuf_size / 2);
}
set_cursor(vc);
@@ -736,6 +739,7 @@ static void visual_init(struct vc_data *vc, int num, int init)
vc->vc_hi_font_mask = 0;
vc->vc_complement_mask = 0;
vc->vc_can_do_color = 0;
+ vc->vc_panic_force_write = false;
vc->vc_sw->con_init(vc, init);
if (!vc->vc_complement_mask)
vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;
@@ -2498,7 +2502,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
goto quit;
}
- if (vc->vc_mode != KD_TEXT)
146 more quoted lines