From 251bd716178bded03694f04a41e9e2cb20cd9fc1 Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Wed, 2 Mar 2016 13:24:14 +0200 Subject: [PATCH] perf/core: Fix perf_sched_count derailment 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Arnaldo Carvalho de Melo Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver 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 --- kernel/events/core.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 5dcc0bd08d11f..b7231498de47f 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8000,6 +8000,9 @@ 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: @@ -8363,8 +8366,6 @@ SYSCALL_DEFINE5(perf_event_open, } } - account_event(event); - /* * Special case software events and allow them to be part of * any hardware group. @@ -8661,8 +8662,6 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, /* Mark owner so we could distinguish it from user events. */ event->owner = TASK_TOMBSTONE; - account_event(event); - ctx = find_get_context(event->pmu, task, event); if (IS_ERR(ctx)) { err = PTR_ERR(ctx); -- 2.39.5