linux-kernel - Re: [PATCH] x86_64: fix delayed signals

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Message-ID: <alpine.LFD.1.10.0807111617470.3459@woody.linux-foundation.org>
Date:	Fri, 11 Jul 2008 16:22:46 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Roland McGrath <roland@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Elias Oltmanns <eo@...ensachen.de>,
	Török Edwin <edwintorok@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Oleg Nesterov <oleg@...sign.ru>
Subject: Re: [PATCH] x86_64: fix delayed signals

On Fri, 11 Jul 2008, Linus Torvalds wrote:
> 
> No, after testing more, I think Edwin is right.

Naah. It is true that there is a huge delay in doing

	ls -l /usr/bin

and then pressing ^C, but after having hit my head against this for a 
while, I realized that it has nothing to do with the kernel.

Doing an "strace ls" showed that ls doesn't play any games with signals 
etc, which fooled me into looking for a kernel reason. 

HOWEVER, it looks like at least fedora does a

	alias ls='ls --color=auto'

and it turns out that if you do that --color=auto, then ls will indeed 
catch all normal signals and set a "please stop now" flag, instead of 
dying immediately. The reason is probably to avoiding leaving the terminal 
with some odd color if interrupted in an inconvenient place.

So I was chasing this latency thing totally unnecessarily. It's in user 
space (or at least _my_ particular issue was).

Other user cases may obviously be elsewhere.

		Linus
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