powerbook/radeon PM problem

[Benjamin Herrenschmidt]

On Thu, 2007-02-01 at 20:11 +0100, Johannes Berg wrote:
> Whenever I resume my powerbook I get:
> 
> [  336.307861] BUG: sleeping function called from invalid context at kernel/rwsem.c:20
> [  336.307871] in_atomic():0, irqs_disabled():1
> [  336.307875] Call Trace:
> [  336.307879] [EC257D30] [C000901C] show_stack+0x3c/0x194 (unreliable)
> [  336.307900] [EC257D60] [C00268B8] __might_sleep+0xd4/0xe8
> [  336.307918] [EC257D70] [C004555C] down_read+0x24/0x5c
> [  336.307930] [EC257D90] [C003A574] blocking_notifier_call_chain+0x20/0x54
> [  336.307940] [EC257DB0] [C017FB60] fb_notifier_call_chain+0x24/0x34
> [  336.307949] [EC257DC0] [C0180178] fb_set_suspend+0x58/0x6c
> [  336.307956] [EC257DE0] [C01A79F0] radeonfb_pci_resume+0x1fc/0x3e0
> [  336.307964] [EC257E00] [C01A7BF8] radeonfb_early_resume+0x24/0x40
> [  336.307970] [EC257E20] [C001A5C0] pmac_call_early_video_resume+0x2c/0x3c
> [  336.307985] [EC257E30] [C01E1148] pmu_ioctl+0x6f8/0xb64
> [  336.307994] [EC257ED0] [C0091C84] do_ioctl+0x80/0x84
> [  336.308003] [EC257EE0] [C0091D0C] vfs_ioctl+0x84/0x43c
> [  336.308009] [EC257F10] [C0092104] sys_ioctl+0x40/0x74
> [  336.308014] [EC257F40] [C00114B4] ret_from_syscall+0x0/0x38
> 
> 
> Hence, there must be a bug somewhere... The documentation to
> fb_set_suspend notes:
> "It must be called with the console semaphore held"

Yeah well, it's -supposed- to be taken by the resume function, but the
early resume path is a hack that runs -really- early (so you get a
screen back for debugging). I should find a way to silence those stupid
warnings...

> So that's one of the bugs, how can that be satisfied when we're just
> resuming and haven't taken that semaphore? (if we did take it, then we'd
> get the warning earlier..)
> 
> Then again, is the resume code really supposed to be called with
> interrupts disabled?

Not normally... but when I wrote that stuff, there was no semaphore
involved in that code path... In fact, the semaphore we are taking
shouldn't be held by anybody else anyway..

> I'm totally unsure what the correct fix for this is.

None other than removing the early wakeup hack :-(

Ben.