From: Eric Wong <normalperson@...>
Date: 2018-04-21T18:02:20+00:00
Subject: [ruby-core:86644] Re: [Ruby trunk Bug#14681] `syswrite': stream closed in another thread (IOError)

samuel@oriontransfer.org wrote:
> Excuse my ignorance, but if you call write, why can't you just
> directly invoke `::write`?  Why do you need to do
> `rb_thread_io_blocking_region`?

rb_thread_io_blocking_region releases the GVL because write(2) may
block on slow filesystem, full pipe/sockets, etc.

We no longer set O_NONBLOCK on sockets/pipes by default since
1.9+; and but that didn't help with slow filesystems whose
buffers are full (or using weird stuff like O_SYNC/O_DIRECT).

rb_thread_io_blocking_region is slightly different than
rb_thread_call_without_gvl because Ruby has traditionally
signaled cross-thread IO#close with IOError instead of undefined
platform-specific behavior (sometimes EBADF, sometimes blocks
for a long time and succeeds, ...).  I'm not sure I actually
agree with this behavior, just stating what things are.

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