[Python-ideas] Async API: some code to review

Richard Oudkerk shibturn at gmail.com
Mon Oct 29 17:41:57 CET 2012

On 29/10/2012 4:09pm, Mark Hackett wrote:
> Is that actually true? It may be guaranteed on Intel x86 compatibles and Linux
> (because of the string operations available in the x86 instruction set), but I
> don't thing anything other than an IPC message has a "you can write a string
> atomically" guarantee. And I may be misremembering that.

The guarantee I was talking about is for pipes on Unix:

POSIX.1-2001 says that write(2)s of less than PIPE_BUF bytes must be 
atomic: the output data is written to the pipe as a contiguous sequence. 
Writes of more than PIPE_BUF bytes may be nonatomic: the kernel may 
interleave the data with data written by other processes. POSIX.1-2001 
requires PIPE_BUF to be at least 512 bytes. (On Linux, PIPE_BUF is 4096 
bytes.) ...

On Windows writes to pipes in message oriented mode are also atomic.

> And even if it's part of the SUS, how do we know this is true for non-UNIX
> compatible systems?

We don't, but that isn't necessarily a reason to ban it as evil.


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