Messages in this thread | | | Subject | Re: powerpc/perf: hw breakpoints return ENOSPC | From | Peter Zijlstra <> | Date | Thu, 16 Aug 2012 09:40:12 +0200 |
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On Thu, 2012-08-16 at 14:23 +1000, Michael Neuling wrote: > > On this second syscall, fetch_bp_busy_slots() sets slots.pinned to be 1, > despite there being no breakpoint on this CPU. This is because the call > the task_bp_pinned, checks all CPUs, rather than just the current CPU. > POWER7 only has one hardware breakpoint per CPU (ie. HBP_NUM=1), so we > return ENOSPC.
I think this comes from the ptrace legacy, we register a breakpoint on all cpus because when we migrate a task it cannot fail to migrate the breakpoint.
Its one of the things I hate most about the hwbp stuff as it relates to perf.
Frederic knows more...
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