perf/core: Fix perf_sched_count derailment

Orabug: 23331015

[ Upstream commit 927a5570855836e5d5859a80ce7e91e963545e8f ]

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: <stable@vger.kernel.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: He Kuang <hekuang@huawei.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 919e67a63aa967566a909f4f6e1c13f8e88cf76e)

Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0eaf3f0b0974a70908fc86f6680b00c3491108ac..66e6568a4736cf9bf8b16400e55ffecad31ec0e1 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7641,6 +7641,9 @@ 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:
@@ -8004,8 +8007,6 @@ SYSCALL_DEFINE5(perf_event_open,
                }
        }
 
-       account_event(event);
-
        /*
         * Special case software events and allow them to be part of
         * any hardware group.
@@ -8270,8 +8271,6 @@ 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);