linux-kernel - Re: [RFC][PATCH 1/5] signals: Always place SIGCONT and SIGSTOP on 'shared

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Message-ID: <20110406130928.GF4142@mtj.dyndns.org>
Date:	Wed, 6 Apr 2011 06:09:28 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Matt Fleming <matt@...sole-pimps.org>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matt Fleming <matt.fleming@...ux.intel.com>
Subject: Re: [RFC][PATCH 1/5] signals: Always place SIGCONT and SIGSTOP on
 'shared_pending'

Hey, guys.

On Wed, Apr 06, 2011 at 02:57:57PM +0200, Oleg Nesterov wrote:
> But even SIGSTOP should be routed properly. If the process is ptraced,
> the tracee reports SIGSTOP to the debugger first. This means that
> tkill(SIGSTOP) should be delivered to the right target.

I think the more important part is that there really isn't much point
in optimizing SIGSTOP/CONT.  They inherently involve heavy,
walk-every-thread operations of putting them to sleep and reversing it
and there isn't much point in optimizing sending SIGSTOP to stopped
processes or CONT to running ones.  In addition, STOP/CONT interaction
is already scary enough so I'd like to avoid adding complexities there
if at all possible.

I think it would be better to concentrate on more usual signals.

Thank you.

-- 
tejun
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