Messages in this thread | | | Date | Thu, 5 Nov 2009 18:32:40 +0000 | From | Alan Cox <> | Subject | Re: [PATCH] pipe: don't block after data has been written |
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> > Welcome to real world. > > Yes in the real world there are bugs. The decision is to choose which > bug you are going to expose. If it was my decision I would make the code > work as documented, as Max wants to do.
Outside of academia the reality is fairly simple. A system needs to behave according to the expected behaviour. That is a mix of things - Standards - Extrapolation (applying the logic of the standard to cases beyond it) - Tradition (things that used to work still work)
If you like: How it is defined to work, how it is expected to work and how it worked last year.
Tradition is a suprisingly large part of it. In the unix world that tradition includes things like "signals do not interrupt disk I/O writes causing short writes".
Pipes however is pretty much pure standards behaviour
In blocking mode they block In non-blocking mode they don't block
Furthermore there are specific rules about writes under a certain size always occurring in an atomic manner.
> In fact I think that Linux will already do short writes if a signal is > received without restart set for the handler. I found several bugs last > year in glibc and libstdc++ fwrite and iostreams regarding that.
The kernel takes great pains not to do this in the cases where tradition dictates otherwise (notably in disk I/O)
Alan
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