Re: broken suspend [Was: 2.6.24-rc2-mm1]

Rafael J. Wysocki
2007-11-19T21:36:18Z

On Monday, 19 of November 2007, Rudolf Marek wrote:
> Hello all,
> >>> gives coretemp_cpu_callback -> coretemp_device_remove ->
> >>> platform_device_unregister, so coretemp seems to be what I have and you don't.
> >
> > Yes.
> >
> > For the coretemp developers: coretemp_cpu_callback() needs to be more
> > careful about what it does. During a system sleep transition (suspend,
> > hibernate, resume) it isn't possible to register or unregister a
> > device. Attempts to register will fail and attempts to unregister will
> > block until the system sleep is over -- and for this callback that
> > means hanging.
>
> Well I wrote the driver. Thanks for the clarification. If I recall correctly I
> looked how this part should be done from others drivers. Now while checking
> what happened to the file, seems Rafael added something related.
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=8bb7844286fb8c9fce6f65d8288aeb09d03a5e0d

Well, in principle you can use the observation that the _FROZEN versions
are used during suspend/hibernation. Thus, if you only unregister the device
for CPU_DEAD, but you won't do that for CPU_DEAD_FROZEN, it will work as long
as the freezer is there.

> > It's not clear what the best way is to fix this. Perhaps the CPU
> > notification should be sent along with a special flag indicating that
> > the CPU transition is part of a system sleep (although this seems
> > racy).

In fact, it's already done that way and I don't think it's racy (see above).

Greetings,
Rafael