Re: [PATCH 3/5] hw-breakpoints: Rewrite the hw-breakpoints layeron top of perf counters
From: K.Prasad
Date: Mon Sep 14 2009 - 13:28:57 EST
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
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perf counters instances.
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The core breakpoint API has changed a bit:
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- register_kernel_hw_breakpoint() now takes a cpu as a parameter. For
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now it doesn't support all cpu wide breakpoints but this may be
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implemented soon.
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- unregister_kernel_hw_breakpoint() and unregister_user_hw_breakpoint()
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have been unified in a single unregister_hw_breakpoint()
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Each breakpoints now match a perf counter which now handles the
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register scheduling, thread/cpu attachment, etc..
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[edited]
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-/*
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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
for all CPUs). As mentioned in my previous mail, this could be
non-trivial lapse in debugging scenarios and even for users like
ksym_tracer in ftrace. Your patch would want to retain the
functionality of load_debug_registers().
Thanks,
K.Prasad
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