From: Robert Klemme <shortcutter@...>
Date: 2011-03-02T19:54:58+09:00
Subject: Re: question: threads behaviour

On Tue, Mar 1, 2011 at 11:13 PM, Eric Wong <normalperson@yhbt.net> wrote:
> Robert Klemme <shortcutter@googlemail.com> wrote:
>> On 03/01/2011 08:16 PM, Eric Wong wrote:
>>> Robert Klemme<shortcutter@googlemail.com>  wrote:
>>>>> 1.8 will schedule other threads if the blocking IO is for a socket/pipe
>>>>> and uses the normal Ruby IO interfaces (or the extension author was
>>>>> careful).  Filesystem I/O (including NFS) can block the entire process
>>>>> in 1.8.
>>>>
>>>> Where do you take that from?  AFAIK internally Ruby 1.8.* uses non
>>>> blocking IO calls in combination with select() to be able to let other
>>>> threads work while IO is under way.
>>>
>>> Yes, I meant "blocking" from a user-visible perspective, not from a
>>> kernel perspective.  If there's an EAGAIN it'll block the current thread
>>> from a user perspective and schedule others using select(), but not
>>> actually block on the syscall that caused EAGAIN.
>>
>> OK, but earlier you said that file system IO can block the entire
>> process - which is not exactly true and also does not match what you
>> said now. :-)
>
> Filesystem IO (regular files) doesn't return EAGAIN (at least not on
> systems I'm familiar with).

http://www.kernel.org/doc/man-pages/online/pages/man2/read.2.html#ERRORS

robert

-- 
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