Re: PATCH Multithreaded core dumps for the 2.5.17 kernel was ....RE: PATCH Multithreaded core dump support for the 2.5.14 (and 15) kernel.

[Pavel Machek <pavel@suse.cz>]

Hi!

> > > Nice. This also closes another issue pointed out: freezing
> > > a process while it is holding the mmap_sem, which may be needed later
> > > while collecting thread registers on IA64.
> > >
> > > Now that Linus has accepted Pavel's swsusp, do you have any thoughts
> > > on using Pavel's scheme to freeze processes?
> >
> > I attempt half of signal delivery to the threads, but that should not be
> > a problem. Currently freezing stuff is there only for CONFIG_SWSUSP case,
> > but it is probably small enough to be there unconditionaly.
> > 								Pavel
> 
> I think that although my tcore_suspend_threads and Pavel's freeze_processes 
> have similar results, I don't think using Pavel's approach for the core dump 
> is a good idea.
> 
> 1) SMP is a stability problem.  I want TCore to work for 2.4x kernels  
> soon. 
> 2) To avoid the issues with I/O bound threads waking up, Pavel's design waits 
> for the signal to get them running and then drops them in the "refrigerator". 
>  
> My design is explicitly going for the most accurate core dump it can.  
> If I need to wait for processes to wake up and get frozen on a large SMB box 
> then we can loose a lot of accuracy.

Okay.

> I do however; think Pavels work could benefit from using some of my approach. 
>  It might simplify all those places where his patch tests p->state | 
> PK_FREEZE and then calls  refrigerator.   It perhaps make it work better for 
> SMP if software suspend is considered a usefull feature on a SMP systems.

swsusp definitely is usable on SMP system. Take server with not-hotpluggable
pci andpci card you want to add. How do you add it with minimum impact on
users?

suspend/add card/resume
									Pavel
PS: I did not yet test swsusp on SMP, through. But I'd like it to work.
-- 
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.