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Date: Sun, 10 Jan 2010 04:10:57 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: Li Zefan <lizf@...fujitsu.com> Cc: prasad@...ux.vnet.ibm.com, Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/4] ksym_tracer: Fix to make the tracer work On Thu, Dec 31, 2009 at 01:54:35PM +0800, Li Zefan wrote: > K.Prasad wrote: > > Frederic must have used for_each_possible_cpu() to account for CPUs that > > are offline at the time of registration, but may eventually turn online. > > Since register_wide_hw_breakpoint() interface is designed to deliver > > system-wide breakpoints, the debug registers of a new online CPU will > > should have the breakpoints populated to comprehensively notify all > > memory accesses over target address. > > > > I'd rather wait to hear from Frederic to know why > > perf_event_create_kernel_counter() returns an error when run for an > > offline cpu and how it can be solved. > > > > See the comment in find_get_context() in kernel/perf_event.c: > > /* > * We could be clever and allow to attach a event to an > * offline CPU and activate it when the CPU comes up, but > * that's for later. > */ > if (!cpu_online(cpu)) > return ERR_PTR(-ENODEV); > > So I think we can use for_each_possible_cpu() in the future, but not now. > Ah, right I indeed missed that. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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