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Date: Sun, 29 Jun 2008 10:09:56 +0300 From: Török Edwin <edwintorok@...il.com> To: Jeremy Fitzhardinge <jeremy@...p.org> CC: 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. Ok. > > That said, if a program is blocking for tens of seconds in block IO, > then that could be a problem in itself. In that case I don't think that a program doing heavy I/O (writeout of 100Mb+) should be able to block other processes waiting for I/O on the same device for tens of seconds. I am using CFQ as I/O scheduler now, I will try the other I/O schedulers (especially deadline) and see if I get better behaviour. Is there any documentation on the tunable values for CFQ? (in Documentation/block there is only about anticipatory and deadline). Best regards, --Edwin -- 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/
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