linux-kernel - Re: getter PTRACE_GETSIGINFO should not modify anything [Re: [PATCH 11/11] ptrace: implement group stop notification for ptracer]

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Message-ID: <20110516130032.GF7128@elte.hu>
Date:	Mon, 16 May 2011 15:00:32 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jan Kratochvil <jan.kratochvil@...hat.com>, oleg@...hat.com,
	vda.linux@...glemail.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	indan@....nu
Subject: Re: getter PTRACE_GETSIGINFO should not modify anything  [Re: [PATCH
 11/11] ptrace: implement group stop notification for ptracer]


* Tejun Heo <tj@...nel.org> wrote:

> Hello,
> 
> On Mon, May 16, 2011 at 02:17:11PM +0200, Jan Kratochvil wrote:
> > On Mon, 16 May 2011 10:43:50 +0200, Tejun Heo wrote:
> > > There's distinction between "broken" and "ugly".  If it's ugly but
> > > functional, you don't need to "fix" it.
> > 
> > The final goal is the user experience (such as the users of GDB), nothing else
> > matters.  If it is so "ugly" the userland developers fail to use it the
> > project as a whole still broken.
> 
> To me, it seems the breakage and mountain of workarounds come more from lack 
> of proper documentation plus the current ptrace + job control + signal 
> interaction which is really broken.  For example, it seems nobody really 
> understood how group stop and ptrace interacts and the different types of 
> traps being used - strace(2) thought the same signal was being delivered 
> twice.

Btw., i'd also like to offer the observation that even these days, running 
brand-new Rawhide distribution with strace-4.5.20-2.fc15.x86_64 and a fresh 
kernel, i *still* often see strace (or ptrace?) misbehavior like it 
misprocessing Ctrl-C and leaving hung threads around which i have to clean up 
manually ...

So if you could bring sanity in here i think we could live with a regression or 
two, if the situation could be improved in the longer run - it's not like we 
are protecting a stable bastion of robust functionality here ...

Thanks,

	Ingo
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