From: "normalperson (Eric Wong)" <normalperson@...>
Date: 2013-10-20T13:16:04+09:00
Subject: [ruby-core:57943] [ruby-trunk - Bug #9036][Open] [PATCH] io.c: make	IO#reopen("pathname") atomic for non-stdio


Issue #9036 has been reported by normalperson (Eric Wong).

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Bug #9036: [PATCH] io.c: make IO#reopen("pathname") atomic for non-stdio
https://bugs.ruby-lang.org/issues/9036

Author: normalperson (Eric Wong)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: ruby 2.1.0dev (2013-10-20 trunk 43369) [x86_64-linux]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


Since rb_sysopen releases the GVL, calling close(fptr->fd) would
leave a window where accessing the file from another thread can hit
IOError on a closed stream

Instead, create a new, temporary FD via rb_sysopen and call
rb_cloexec_dup2 on it to atomically replace the file fptr->fd points
to.  This leaves no possible window where fptr->fd is invalid to
userspace (even for any threads running w/o GVL).

Without this patch, I need to maintain separate code paths for
atomically reopening (e.g. log rotation) std{in,out,err} vs
other files in a multithreaded application.



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