Messages in this thread | | | Date | Fri, 24 Mar 2017 15:23:29 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI |
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On Fri, Mar 24, 2017 at 02:15:16PM +0000, Liang, Kan wrote: > > > > On Thu, 23 Mar 2017, Peter Zijlstra wrote: > > > On Thu, Mar 23, 2017 at 11:25:49AM -0700, kan.liang@intel.com wrote: > > > > + for_each_possible_cpu(cpu) { > > > > + rdmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, > > &debugctlmsr); > > > > + if (val) > > > > + wrmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, > > debugctlmsr | DEBUGCTLMSR_FREEZE_WHILE_SMM); > > > > + else > > > > + wrmsrl_on_cpu(cpu, MSR_IA32_DEBUGCTLMSR, > > debugctlmsr & ~DEBUGCTLMSR_FREEZE_WHILE_SMM); > > > > + } > > > > > > No; that's just disgusting. Also {rd,wr}msr_on_cpu() should die, > > > exactly because people end up writing crap like this. > > > > Aside of that this is completely broken against other users of > > DEBUGCTLMSR because it's not atomic vs. the other modifications. > > > > OK. I will change it. > I guess I need a way/function which can atomically rd,wr msr on all cpus. > Are there existing alternative ways/functions to do that?
No; also don't forget hotplug.
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