Bug 738665 – strange pthread/fork deadlock

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Bug 738665 - strange pthread/fork deadlock

Summary:	strange pthread/fork deadlock

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 6
Classification:	Red Hat
Component:	glibc (Show other bugs)
Sub Component:
Version:	6.0
Hardware:	All Linux

Priority	unspecified Severity unspecified
Target Milestone:	rc
Target Release:	---
Assigned To:	Andreas Schwab
QA Contact:	qe-baseos-tools
Docs Contact:

URL:
Whiteboard:
Keywords:

Depends On:
Blocks:	743047
	Show dependency tree / graph

Reported:	2011-09-15 09:49 EDT by Andreas Schwab
Modified:	2017-02-09 06:19 EST (History)
CC List:	3 users (show)

See Also:
Fixed In Version:	glibc-2.12-1.42.el6
Doc Type:	Bug Fix
Doc Text:
Story Points:	---
Clone Of:	737387
Clones:	759341 (view as bug list)
Environment:
Last Closed:	2011-12-06 12:48:13 EST
Type:	---
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Sourceware	13699	None	None	None	2017-02-09 06:19 EST
Red Hat Product Errata	RHSA-2011:1526	normal	SHIPPED_LIVE	Low: glibc security, bug fix, and enhancement update	2011-12-05 20:02:21 EST

Groups: None (edit)

Description Andreas Schwab 2011-09-15 09:49:16 EDT

+++ This bug was initially created as a clone of Bug #737387 +++

Created attachment 522617 [details]
test case demonstrating the issue

There appears to be a strange bug in glibc that causes deadlocks when calling fork() from threads. We had a testcase in GLib failing from time to time because of this.

I've attached a minimal testcase that uses only pure pthreads + libc. Compile it with -pthread and run it. It should fill your screen with dots for a while, then hang when it hits the bug (which happens randomly anywhere between 1 dot and hundreds). I've already received independent verification that this testcase hangs on several people's computers.

I believe this to be an upstream issue since this bug is visible on Ubuntu as well, but the glibc website says I should file bugs against distributions first. I also believe the issue to be a regression since older Fedora and RHEL releases are unaffected.  The problem appears to affect both 32 and 64bits.
Description of problem:

Some notes:

 - compiling the testcase with -static has the side-effect of causing the
   bug to go away

 - compiling the testcase with -DFORK_DIRECTLY also appears to solve the
   problem

 - replacing the execv() with a direct exit(0) doesn't solve the problem
   but causes the frequency to change

The fact that both static linking and making the fork() syscall directly cause the problem to disappear leads me to believe that this is a libc bug rather than a kernel bug (which is the only other possibility). I'm not 100% sure of that, though, since libc actually uses the clone() syscall to implement fork(), so there could be a different inside the kernel because of that.

Comment 4 Shane Carr 2011-12-01 21:25:13 EST

We are hitting this bug regularly in RHEL5 (glibc 2.5).  I have confirmed that the attached test case hangs on multiple machines.

Is there any chance of having the fix integrated into RHEL5?

Comment 5 errata-xmlrpc 2011-12-06 12:48:13 EST

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1526.html

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