[ruby-core:89950] [Ruby trunk Bug#14968] [PATCH] io.c: make all pipes nonblocking by default

[ko1@atdot.net]

Issue #14968 has been updated by ko1 (Koichi Sasada).


Honestly speaking, we are not sure we can introduce it into Ruby 2.6 (incompatibility, stability and so on).

So please commit it and let's try it.
If we find troubles we can't solve, we may revert them.

Thanks,
Koichi


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Bug #14968: [PATCH] io.c: make all pipes nonblocking by default
https://bugs.ruby-lang.org/issues/14968#change-75044

* Author: normalperson (Eric Wong)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
Crap, I always planned to have something like this for [Feature #13618]
(auto-Fiber); but introducing a race condition for Timer-thread
elimination in [Misc #14937] forced me to introduce this early.

Anyways, I might have to revert and reintroduce timer-thread if this
change is unnacceptable :<  (I HATE timer thread)

```
io.c: make all pipes nonblocking by default

All normal Ruby IO methods (IO#read, IO#gets, IO#write, ...) are
all capable of appearing to be "blocking" when presented with a
file description with the O_NONBLOCK flag set; so there is
little risk of incompatibility within Ruby-using programs.

The biggest compatibility risk is when spawning external
programs.  As a result, stdin, stdout, and stderr are now always
made blocking before exec-family calls.

Timer-thread elimination in https://bugs.ruby-lang.org/issues/14937
introduced a race condition in signal handling.  It is possible
to receive a signal inside BLOCKING_REGION right before read/write
syscalls.  If this patch cannot be accepted, I will have to revert
to reintroduce timer-thread and increase resource use (which
led to other failures in the past).  The race condition
introduced for [Misc #14937] led to rare CI failures on a few
tests:

- test/ruby/test_thread.rb (test_thread_timer_and_interrupt):
  http://www.rubyist.net/~akr/chkbuild/debian/ruby-trunk/log/20180805T080500Z.fail.html.gz

- test/ruby/test_io.rb (test_race_gets_and_close):
  http://ci.rvm.jp/results/trunk@P895/1190369

This change is ALSO necessary to take advantage of (proposed
lightweight concurrency (aka "auto-Fiber") or any similar
proposal: https://bugs.ruby-lang.org/issues/13618

TODO: all sockets and FIFOs non-blocking by default, too
```


---Files--------------------------------
0001-io.c-make-all-pipes-nonblocking-by-default.patch (12.1 KB)


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