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From: Roland McGrath <roland@redhat.com>
To: David Smith <dsmith@redhat.com>
Cc: Maynard Johnson <maynardj@us.ibm.com>,
	systemtap@sourceware.org,
	        "Frank Ch. Eigler" <fche@redhat.com>
Subject: Re: Backward compatibility for insn probe point
Date: Wed, 13 May 2009 18:24:00 -0000	[thread overview]
Message-ID: <20090513182359.0CF33FC35D@magilla.sf.frob.com> (raw)
In-Reply-To: David Smith's message of  Wednesday, 13 May 2009 10:04:25 -0500 <4A0AE179.9050801@redhat.com>

> I poked around the kernel source some more, but couldn't see what was
> going wrong.  

I figured you'd use some stap probes to follow the code paths!

> I've changed the itrace code to stop the task after each step trap (so
> that it acts more like ptrace).  I've tested this on several kernels
> (2.6.18-141.el5/ppc, 2.6.18-128.1.10.el5/x86_64/i686, and
> 2.6.25-14.fc9.ppc64) and it seems to work correctly.
> 
> Does this seem like a reasonable work-around?  Could there be problems
> with this approach?

I presume it kills performance.  But what works works, that's a what a
work-around is.  I'd hope that you don't make it use this "not really
right" mode for kernels with the modern utrace interface that doesn't have
this bug.


Thanks,
Roland

  reply	other threads:[~2009-05-13 18:24 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-04-01 21:59 Maynard Johnson
2009-04-27 21:01 ` David Smith
2009-04-29 13:56   ` Maynard Johnson
2009-04-29 21:08   ` Maynard Johnson
2009-04-30 18:00     ` David Smith
2009-04-30 20:48       ` Roland McGrath
2009-05-12 16:06         ` David Smith
2009-05-12 18:20           ` Roland McGrath
2009-05-13 15:04             ` David Smith
2009-05-13 18:24               ` Roland McGrath [this message]
2009-05-14 15:11                 ` David Smith
2009-05-14 18:41                   ` Roland McGrath
2009-05-14 19:01                   ` Maynard Johnson
2009-05-14 19:44                     ` David Smith
2009-05-14 21:36                       ` David Smith
2009-05-15 13:52                         ` ia64 hang when using itrace (was Re: Backward compatibility for insn probe point) David Smith

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