From: Peter Zijlstra <peterz@infradead.org>
To: "Liang, Kan" <kan.liang@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"acme@kernel.org" <acme@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"eranian@google.com" <eranian@google.com>,
"jolsa@kernel.org" <jolsa@kernel.org>,
"ak@linux.intel.com" <ak@linux.intel.com>
Subject: Re: [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI
Date: Fri, 24 Mar 2017 15:23:29 +0100 [thread overview]
Message-ID: <20170324142329.lclrwpy5kuo4ekua@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077536C3CCB@SHSMSX103.ccr.corp.intel.com>
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.
next prev parent reply other threads:[~2017-03-24 14:23 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-23 18:25 [PATCH 0/3]measure SMI cost kan.liang
2017-03-23 18:25 ` [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI kan.liang
2017-03-23 20:31 ` Peter Zijlstra
2017-03-23 20:48 ` Liang, Kan
2017-03-23 22:23 ` Andi Kleen
2017-03-24 8:16 ` Peter Zijlstra
2017-03-23 20:32 ` Peter Zijlstra
2017-03-24 8:31 ` Thomas Gleixner
2017-03-24 14:15 ` Liang, Kan
2017-03-24 14:23 ` Peter Zijlstra [this message]
2017-03-23 18:25 ` [PATCH 2/3] tools lib api fs: Add sysfs__write_int function kan.liang
2017-03-28 3:38 ` Elliott, Robert (Persistent Memory)
2017-03-23 18:25 ` [PATCH 3/3] perf stat: Add support to measure SMI cost kan.liang
2017-03-24 8:44 ` [PATCH 0/3]measure " Thomas Gleixner
2017-03-24 11:40 ` Andi Kleen
2017-03-24 12:07 ` Thomas Gleixner
2017-03-24 14:14 ` Liang, Kan
2017-03-31 21:51 ` Stephane Eranian
2017-04-01 1:41 ` Liang, Kan
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