linux-kernel - Re: [tip:perf/core] perf/core: Verify we have a single perf_hw

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Date:	Mon, 4 Apr 2016 16:02:08 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	torvalds@...ux-foundation.org, jolsa@...hat.com,
	vincent.weaver@...ne.edu, alexander.shishkin@...ux.intel.com,
	linux-kernel@...r.kernel.org, mingo@...nel.org, acme@...hat.com,
	tglx@...utronix.de, eranian@...gle.com, hpa@...or.com
Cc:	linux-tip-commits@...r.kernel.org, bp@...e.de
Subject: Re: [tip:perf/core] perf/core: Verify we have a single
 perf_hw_context PMU

On Thu, Mar 31, 2016 at 02:23:20AM -0700, tip-bot for Peter Zijlstra wrote:
> Commit-ID:  26657848502b78474a5f17f9ce2ae6dc8d8d6262
> Gitweb:     http://git.kernel.org/tip/26657848502b78474a5f17f9ce2ae6dc8d8d6262
> Author:     Peter Zijlstra <peterz@...radead.org>
> AuthorDate: Tue, 22 Mar 2016 22:09:18 +0100
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Thu, 31 Mar 2016 10:30:41 +0200
> 
> perf/core: Verify we have a single perf_hw_context PMU
> 
> There should (and can) only be a single PMU for perf_hw_context
> events.
> 
> This is because of how we schedule events: once a hardware event fails to
> schedule (the PMU is 'full') we stop trying to add more. The trivial
> 'fix' would break the Round-Robin scheduling we do.


This triggered on AMD machines..

---
Subject: perf,amd: Do not register a task ctx for uncore PMUs

Uncore PMUs are per node, they cannot have per-task counters.

Reported-by: Borislav Petkov <bp@...e.de>
Reported-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/events/amd/uncore.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index 3db9569..98ac573 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -263,6 +263,7 @@ static const struct attribute_group *amd_uncore_attr_groups[] = {
 };
 
 static struct pmu amd_nb_pmu = {
+	.task_ctx_nr	= perf_invalid_context,
 	.attr_groups	= amd_uncore_attr_groups,
 	.name		= "amd_nb",
 	.event_init	= amd_uncore_event_init,
@@ -274,6 +275,7 @@ static struct pmu amd_nb_pmu = {
 };
 
 static struct pmu amd_l2_pmu = {
+	.task_ctx_nr	= perf_invalid_context,
 	.attr_groups	= amd_uncore_attr_groups,
 	.name		= "amd_l2",
 	.event_init	= amd_uncore_event_init,