Bug #9036: [PATCH] io.c: make IO#reopen("pathname") atomic for non-stdio

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.1.0dev (2013-10-20 trunk 43369) [x86_64-linux]
• Backport: 2.0.0: DONE, 2.1: DONTNEED

[normalperson (Eric Wong)]

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.

[normalperson (Eric Wong)]

"normalperson (Eric Wong)" [e-mail] wrote:

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.

Separate code paths like this:
http://bogomips.org/yahns.git/patch/?id=bcb10abe5
(review greatly appreciated!, thanks!)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

This issue was solved with changeset r43373.
Eric, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

io.c: make IO#reopen("pathname") atomic

• io.c (rb_io_reopen): 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). based on the
  patch by Eric Wong [e-mail] at [ruby-core:57943].
  [Bug #9036]

[naruse (Yui NARUSE)]

• Backport changed from 1.9.3: UNKNOWN, 2.0.0: UNKNOWN to 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED to 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: DONTNEED

r43373 was already included in ruby_2.1.

[usa (Usaku NAKAMURA)]

• Backport changed from 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: DONTNEED to 2.0.0: DONE, 2.1: DONTNEED

backported into ruby_2_0_0 at r47545.