[PATCH V2 1/6] perf/core: Add sanity check to deal with pinned event failure

From: Reinette Chatre <reinette.chatre@intel.com>
To: tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com,
	peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
	vikas.shivappa@linux.intel.com
Cc: gavin.hindman@intel.com, jithu.joseph@intel.com,
	dave.hansen@intel.com, hpa@zytor.com, x86@kernel.org,
	linux-kernel@vger.kernel.org,
	Reinette Chatre <reinette.chatre@intel.com>
Subject: [PATCH V2 1/6] perf/core: Add sanity check to deal with pinned event failure
Date: Thu, 16 Aug 2018 13:16:04 -0700	[thread overview]
Message-ID: <6a54e5c43aca477db9957e083024701bd199b7ab.1534450299.git.reinette.chatre@intel.com> (raw)
In-Reply-To: <cover.1534450299.git.reinette.chatre@intel.com>
In-Reply-To: <cover.1534450299.git.reinette.chatre@intel.com>

It is possible that a failure can occur during the scheduling of a
pinned event. The initial portion of perf_event_read_local() contains
the various error checks an event should pass before it can be
considered valid. Ensure that the potential scheduling failure
of a pinned event is checked for and have a credible error.

Link: http://lkml.kernel.org/r/20180807093615.GY2494@hirez.programming.kicks-ass.net
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
 kernel/events/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 80cca2b30c4f..005d0f2519fd 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3940,6 +3940,12 @@ int perf_event_read_local(struct perf_event *event, u64 *value,
 		goto out;
 	}
 
+	/* If this is a pinned event it must be running on this CPU */
+	if (event->attr.pinned && event->oncpu != smp_processor_id()) {
+		ret = -EBUSY;
+		goto out;
+	}
+
 	/*
 	 * If the event is currently on this CPU, its either a per-task event,
 	 * or local to this CPU. Furthermore it means its ACTIVE (otherwise
-- 
2.17.0

