linux-kernel - Re: Ctrl+C doesn't interrupt process waiting for I/O

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Message-ID: <48673873.6040202@davidnewall.com>
Date:	Sun, 29 Jun 2008 16:53:31 +0930
From:	David Newall <davidn@...idnewall.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Török Edwin <edwintorok@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Ctrl+C doesn't interrupt process waiting for I/O

Jeremy Fitzhardinge wrote:
> Török Edwin wrote:
>> ...
>> - I have a (I/O bound) process running in my terminal, and I want to
>> interrupt it with Ctrl+C
>>  - I type Ctrl+C several times, and the process is not interrupted for
>> several seconds (10-30 secs)
>>  - if I type Ctrl+Z, and use kill %1 the process dies faster than
>> waiting for it to react to Ctrl+C  
>
> Yes, it's intended behaviour.  Filesystem IO syscalls are considered
> "fast" and are interruptible.  Usermode code can reasonably expect
> that file IO will never return EINTR.

This does not address the symptom that the process can be killed quicker
by sending a SIGTERM.  I've noticed the problem, too (2.6.25.)  I wonder
if it isn't some strangeness in the tty layer (hence the interrupt key
is slower than an explicitly sent signal.)
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