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Date: Thu, 5 Jul 2001 16:53:33 -0700 (PDT)
From: Nathan Mower <nmower@verio.net>
To: freebsd-gnats-submit@FreeBSD.org
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Subject: i386/28746: Race condition in run-time linker
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>Number:         28746
>Category:       i386
>Synopsis:       Race condition in run-time linker
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jul 05 17:00:03 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     Nathan Mower
>Release:        4.2
>Organization:
Verio
>Environment:
FreeBSD ft.iserver.com 4.2-RELEASE FreeBSD 4.2-RELEASE #2a: Thu Jun 28 11:27:27 MDT 2001 root@fc:/usr/src/sys/compile/VKERN  i386

>Description:
There seems to be a race condition in the run-time linker (ELF).  As
near as I can tell, the situation is this: _rtld_bind calls
rlock_acquire(), but before it gets to rlock_release(), a signal is
caught.  The signal handler calls exit(), so the __atexit list is
traversed, calling rtld_exit(), which calls wlock_acquire().  This
spins on the lock, which it never gets.  The process is hung.
>How-To-Repeat:
Heavy traffic on Apache web server (I use torture.pl).  Frequently send
SIGUSR1 to child Apache processes.  This is a very intermittent bug,
as you can well imagine.
>Fix:
Known work-around: run Apache with LD_BIND_NOW turned on.  I dunno --
might have to block signals between rlock_acquire() and rlock_release()
in _rtld_bind().
>Release-Note:
>Audit-Trail:
>Unformatted:

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