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Date:      Wed, 17 Jun 2009 18:58:49 -0400
From:      Wesley Shields <wxs@FreeBSD.org>
To:        Thomas Backman <serenity@exscape.org>
Cc:        freebsd-current@freebsd.org
Subject:   Re: DTrace panic while probing syscall::open (and possibly many others)
Message-ID:  <20090617225849.GB28509@atarininja.org>
In-Reply-To: <20090522200306.GE2630@atarininja.org>
References:  <949B5884-5303-4EFF-AC7D-293640FFA012@exscape.org> <0C235698-3ED2-4AE9-A7D1-5DC56D8324A4@exscape.org> <200905212129.47892.mel.flynn%2Bfbsd.current@mailing.thruhere.net> <44F486FA-E798-448D-BE31-F7A51EF1F612@exscape.org> <60173AF0-7E54-4BDD-8927-0DADA9DAD1B4@exscape.org> <20090522200306.GE2630@atarininja.org>

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On Fri, May 22, 2009 at 04:03:06PM -0400, Wesley Shields wrote:
> On Fri, May 22, 2009 at 10:00:56AM +0200, Thomas Backman wrote:
> > On May 22, 2009, at 09:31 AM, Thomas Backman wrote:
> > >
> > > ...
> > > dtrace: error on enabled probe ID 1 (ID 38977: syscall::open:entry):  
> > > invalid address (0xffffff803e9afae0) in action #1 at DIF offset 28
> > > dtrace: error on enabled probe ID 1 (ID 38977: syscall::open:entry):  
> > > invalid address (0xffffff803e9afae0) in action #1 at DIF offset 28
> > > dtrace: error on enabled probe ID 1 (ID 38977: syscall::open:entry):  
> > > invalid address (0xffffff803e9afae0) in action #1 at DIF offset 28
> > >
> > 
> > Actually, I still get these. Bummer.
> > 
> > [root@chaos /usr/local/sbin]# execsnoop
> >    UID    PID   PPID ARGS
> >      0   1931   1924 /bin/sh
> >      0   1931   1924 /bin/sh
> >      0   1932   1931 /bin/mkdir
> >      0   1932   1931 /bin/mkdir
> > dtrace: error on enabled probe ID 2 (ID 39086:  
> > syscall::execve:return): invalid address (0xffffff803e8cfae0) in  
> > action #8
> > dtrace: error on enabled probe ID 3 (ID 39086:  
> > syscall::execve:return): invalid address (0xffffff803e8cfae0) in  
> > action #8
> >      0   1944   1933 mktemp
> >      0   1944   1933 mktemp
> > dtrace: error on enabled probe ID 2 (ID 39086:  
> > syscall::execve:return): invalid address (0xffffff803ea58ae0) in  
> > action #8
> > dtrace: error on enabled probe ID 3 (ID 39086:  
> > syscall::execve:return): invalid address (0xffffff803ea58ae0) in  
> > action #8
> > dtrace: error on enabled probe ID 2 (ID 39086:  
> > syscall::execve:return): invalid address (0xffffff803ea9eae0) in  
> > action #8
> > dtrace: error on enabled probe ID 3 (ID 39086:  
> > syscall::execve:return): invalid address (0xffffff803ea9eae0) in  
> > action #8
> >      0   1948   1947 /bin/sh
> >      0   1948   1947 /bin/sh
> >      0   1949   1948 vnstat
> >      0   1949   1948 vnstat
> >      0   1950   1933 /bin/rm
> >      0   1950   1933 /bin/rm
> >      0   1951   1907 /bin/sh
> >      0   1951   1907 /bin/sh
> >      0   1952   1951 make
> >      0   1952   1951 make
> > 
> > (No idea why everything is printed twice either.)
> > Also, the DTrace variable "walltimestamp" seems to return "1970 Jan  1  
> > 01:00:00" (I'm in GMT+2 right now, btw) every time.
> 
> This leads me to believe it's a race somewhere.
> 
> Another datapoint: whatever was changed also made it into 7.2 as that is
> broken in the same fashion. I just installed a 7.1 VM and tried it there
> and it works.

I just updated a -current machine to r194361 and the race condition is
still there but not triggered as often, and it no longer leads to a
panic. I still get occasional output like what is listed above but no
panic.

-- WXS



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