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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <486704AC.2090207@qumranet.com>
Date:	Sun, 29 Jun 2008 06:42:36 +0300
From:	Avi Kivity <avi@...ranet.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:
>> Hi,
>>
>> I have encountered the following situation several times, but I've been
>> unable to come up with a way to reproduce this until now:
>>  - some process is keeping the disk busy (some cron job for example:
>> updatedb, chkrootkit, ...)
>>  - other processes that want to do I/O have to wait (this is normal)
>>  - 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
>>
>> This issue occurs both on my x86-64 machine that uses reiserfs, and on
>> my x86 machine that uses XFS, so it doesn't seem related to the
>> underlying FS.
>> I use 2.6.25-2 and 2.6.26-rc8 now; I don't recall seeing this behaviour
>> with old kernels (IIRC I see this since 2.6.21 or 2.6.23).
>>
>> Is this intended behaviour, or should I report a bug?
>>   
>
> 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.

That's filesystem dependent; if you mount an nfs filesystem with the 
'intr' mount option, it will be interruptible (which makes sense, as it 
is impossible to guarantee the server's responsiveness).

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/