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[4.2.y-ckt,stable] Patch "perf/core: Fix perf_sched_count derailment" has been added to the 4.2.y-ckt tree

Message ID 1459381901-2457-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa March 30, 2016, 11:51 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    perf/core: Fix perf_sched_count derailment

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

From 34812019868aca1c40a4bb0ef6298e46c1738420 Mon Sep 17 00:00:00 2001
From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Date: Wed, 2 Mar 2016 13:24:14 +0200
Subject: perf/core: Fix perf_sched_count derailment

commit 927a5570855836e5d5859a80ce7e91e963545e8f upstream.

The error path in perf_event_open() is such that asking for a sampling
event on a PMU that doesn't generate interrupts will end up in dropping
the perf_sched_count even though it hasn't been incremented for this
event yet.

Given a sufficient amount of these calls, we'll end up disabling
scheduler's jump label even though we'd still have active events in the
system, thereby facilitating the arrival of the infernal regions upon us.

I'm fixing this by moving account_event() inside perf_event_alloc().

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/1456917854-29427-1-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 kernel/events/core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--
2.7.4
diff mbox

Patch

diff --git a/kernel/events/core.c b/kernel/events/core.c
index d86859f..ca03e01 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7672,6 +7672,9 @@  perf_event_alloc(struct perf_event_attr *attr, int cpu,
 		}
 	}

+	/* symmetric to unaccount_event() in _free_event() */
+	account_event(event);
+
 	return event;

 err_per_task:
@@ -8035,8 +8038,6 @@  SYSCALL_DEFINE5(perf_event_open,
 		}
 	}

-	account_event(event);
-
 	/*
 	 * Special case software events and allow them to be part of
 	 * any hardware group.
@@ -8296,8 +8297,6 @@  perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
 	/* Mark owner so we could distinguish it from user events. */
 	event->owner = EVENT_OWNER_KERNEL;

-	account_event(event);
-
 	ctx = find_get_context(event->pmu, task, event);
 	if (IS_ERR(ctx)) {
 		err = PTR_ERR(ctx);