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

[Török Edwin]

Jeremy Fitzhardinge wrote:
> Avi Kivity wrote:
>> Applications should not assume that write() (or other syscalls) can't
>> return EINTR.  Not all filesystems have a bounded-time backing store.
>
> The distinction between 'fast' (filesystem) and 'slow' (terminals and
> pipes) blocking syscalls goes back to the earliest days of Unix, and
> is part of the ABI.  Most filesystem syscalls are not documented to
> ever return EINTR.

POSIX documents EINTR for write(), and the manpage on my Linux distro
says the same.
However I don't think introducing EINTR would be beneficial (it will
likely cause applications that don't expect it to break).

>
>> 'soft' has its own problems; namely false positives when someone
>> steps on the network cable, temporarily blocking packet flow, or when
>> using a clustered server which may take some time to recover from a
>> fault.
>
> Sure.  It's the basic problem of trying to make network access
> transparent by hiding the failure modes.  You either need to put up
> with spurious timeouts caused by transient failures, or unbounded
> blocking on real failures.
>
> Regardless, NFS is the exception here, and making normal block-backed
> filesystems start throwing EINTRs around would be a huge behavioural
> change.

Agreed.

Best regards,
--Edwin
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