Re: [PATCH 3/5] hw-breakpoints: Rewrite the hw-breakpoints layeron top of perf counters
From: Frederic Weisbecker
Date: Mon Sep 14 2009 - 17:36:16 EST
On Mon, Sep 14, 2009 at 10:58:35PM +0530, K.Prasad wrote:
>
On Thu, Sep 10, 2009 at 10:29:25AM +0200, Frederic Weisbecker wrote:
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> This patch rebase the implementation of the breakpoints API on top of
>
> perf counters instances.
>
>
>
> The core breakpoint API has changed a bit:
>
>
>
> - register_kernel_hw_breakpoint() now takes a cpu as a parameter. For
>
> now it doesn't support all cpu wide breakpoints but this may be
>
> implemented soon.
>
>
>
> - unregister_kernel_hw_breakpoint() and unregister_user_hw_breakpoint()
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> have been unified in a single unregister_hw_breakpoint()
>
>
>
> Each breakpoints now match a perf counter which now handles the
>
> register scheduling, thread/cpu attachment, etc..
>
>
>
[edited]
>
>
>
> -/*
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> - * Load the debug registers during startup of a CPU.
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> - */
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> -void load_debug_registers(void)
>
>
It does not appear that perf handles CPUs that come up new (if else,
>
blame my understanding of find_get_context():-)) and hence post breakpoint
>
integration, the new CPUs wouldn't contain any breakpoint values (meant
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for all CPUs). As mentioned in my previous mail, this could be
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non-trivial lapse in debugging scenarios and even for users like
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ksym_tracer in ftrace. Your patch would want to retain the
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functionality of load_debug_registers().
>
>
Thanks,
>
K.Prasad
>
Ah it seems it can.
Look at:
static void __perf_counter_exit_cpu(void *info)
static void perf_counter_exit_cpu(int cpu)
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