Re: [BUG REPORT] perf tools: x86_64: Broken calllchain when sampling taken at 'callq' instruction

[Wangnan (F)]

On 2015/11/19 14:37, Ingo Molnar wrote:
> * Wangnan (F) <wangnan0@xxxxxxxxxx> wrote:
>
> > > perf cmdline is
> > >
> > > # ./pref record  -g -F 9 --call-graph dwarf ./test_dwarf_unwind
> > >
> > > Use default events, precise_ip == 2 so uses PEBS.
> > Testetd 'cycles', 'cycles:p' and 'cycles:pp'. Only 'cycles:pp' captures
> > sample at callq. So maybe a PEBS problem?
> Well, that's how our PEBS sampling works: we roll back the instruction pointer to
> point at the instruction generating the sample. The state itself is
> post-instruction.

Just for curiosity:

how the interrupted process continue to execute, when the PC
saved in pt_regs still pointed to 'callq' but SP and stack has
already changes? Do we fix it in kernel, or by hardware?

Thank you.

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