Re: swsusp console change/userspace hang

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2005-08-29 at 01:26 +0100, Matthew Garrett wrote:
> Hi!
> 
> I'm currently working on an entirely userspace bootsplash program. It 
> works quite happily, except in the case of resuming from hibernation. 
> The splash program is launched at the start of initramfs, and at the 
> end of initramfs (after the disk modules have been loaded) we attempt to 
> trigger resume from userspace.
> 
> The code registers a signal that's fired on VT change. If a console
> change is requested when it's currently drawing, it disables drawing and
> schedules an alarm to fire 0.1 seconds later in order to avoid switching
> the console when part-way through a framebuffer operation.
> 
> The problem seems to be that swsusp tries to change the console and then 
> immediately freezes userspace. For reasons I don't entirely understand, 
> this freezes the machine. If I remove the pm_prepare_console call from 
> pm_prepare_processes, resume functions correctly.

Hrm.. it uses pm_prepare_console(), which should wait for the console to
become active... However, it calls vt_waitactive without dealing with
-EINTR. You might be getting a signal or something, can you check what's
going on inside pm_prepare_console ?

> For now I'll probably just work around this by removing the console 
> change from our kernels (we can do that in userspace scripting instead), 
> but this still seems to be a less than ideal situation - I'm guessing 
> that the same would happen if we were displaying the splash on suspend. 
> Any ideas what might be causing this, and how to rectify it?