Messages in this thread | | | Subject | Re: Ctrl+C doesn't interrupt process waiting for I/O | From | Andi Kleen <> | Date | Sun, 29 Jun 2008 14:10:42 +0200 |
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Jeremy Fitzhardinge <jeremy@goop.org> writes:
>> 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 said, if a program is blocking for tens of seconds in block IO, > then that could be a problem in itself.
Still there's the effect that Ctrl-Z+kill works faster than Ctrl-C that is not explained by this. This has often annoyed me too. I'm not sure why it is. In theory they should be the same unless someone blocks SIGINT.
-Andi
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