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[Bug runtime/11641] FAIL: fib (19 1) backtrace from uretprobe fails
- From: "wenji dot huang at oracle dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 12 Jun 2010 03:03:00 -0000
- Subject: [Bug runtime/11641] FAIL: fib (19 1) backtrace from uretprobe fails
- References: <20100528110745.11641.mjw@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From wenji dot huang at oracle dot com 2010-06-12 03:03 -------
(In reply to comment #7)
> > The reference of GET_PC_URETPROBE_NONE in stack.c is guarded by
> > STAPCONF_UPROBE_GET_PC. As for others in uprobe/*, seems not necessary.
>
> But there is another reference in tapsets.cxx.
>
> > I tried the patch on FC13 and upstream linus kernel. No building break found.
>
> Yes, but I was referring to the utrace-less uprobes variant.
>
> But anyway, I'd like to understand why this patch makes a difference.
> What code behaves differently for a kretprobe_instance* == 0 vs -1, and why?
>
Frankly speaking, I don't understand it well. Maybe the following code affects
the execution.
The function uprobe_get_pc, will check ri==0, then switch to different path.
But in caller __stp_stack_print (stack-i386.c), it will invoke uprobe_get_pc
only when ri!=0.
So guess some cases are missing.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=11641
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