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From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: kan.liang@intel.com, mingo@redhat.com, acme@kernel.org,
	linux-kernel@vger.kernel.org, eranian@google.com,
	jolsa@kernel.org, ak@linux.intel.com
Subject: Re: [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI
Date: Fri, 24 Mar 2017 09:31:25 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1703240929030.3688@nanos> (raw)
In-Reply-To: <20170323203255.kps67homffxhl3cv@hirez.programming.kicks-ass.net>

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.

Thanks,

	tglx

  reply	other threads:[~2017-03-24  8:34 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 [this message]
2017-03-24 14:15       ` Liang, Kan
2017-03-24 14:23         ` Peter Zijlstra
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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