When javaFrameAnchor::_last_Java_sp == NULL for a non-first entry frame

Xiaobin Lu Xiaobin.Lu at Sun.COM
Thu Nov 19 18:42:04 PST 2009

I don't think I know why _last_Java_sp is NULL. However, to explain why 
you saw different stack pointer value on different Linux environment, 
take a look at os_linux.cpp, there are about 40 lines of comments 
talking about "thread stack" related things on different Linux 


On 11/19/09 18:10, Hiroshi Yamauchi wrote:
> Hi,
> In AsyncGetCallTrace, I observe
>   javaFrameAnchor::_last_Java_sp == NULL
> in non-first entry frames on Linux/x86. It is the condition for the
> entry frame to be a first frame. So, I get truncated stack traces
> because stack walk stops at the false first frame.
> I thought that the contract was that the _last_Java_sp != NULL for all
> non-first entry frames. Is it correct?
> Strangely I see the behavior on one Linux environment (kernel, libc,
> other libraries) but not on another Linux environment (Ubuntu). But
> I'm not sure how the environment could affect the _last_Java_sp field.
> Does it ring anyone's bell?
> thanks.
> Hiroshi

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