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[Bug runtime/11641] FAIL: fib (19 1) backtrace from uretprobe fails

------- 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.


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