From f38b082081bf69a06fffb8b32a175999e2320c5b Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Tue, 2 Jun 2009 21:05:16 +1000 Subject: [PATCH] perf_counter: Initialize per-cpu context earlier on cpu up This arranges for perf_counter's notifier for cpu hotplug operations to be called earlier than the migration notifier in sched.c by increasing its priority to 20, compared to the 10 for the migration notifier. The reason for doing this is that a subsequent commit to convert the cpu migration counter to use the generic swcounter infrastructure will add a call into the perf_counter subsystem when tasks get migrated. Therefore the perf_counter subsystem needs a chance to initialize its per-cpu data for the new cpu before it can get called from the migration code. This also adds a comment to the migration notifier noting that its priority needs to be lower than that of the perf_counter notifier. Signed-off-by: Paul Mackerras Cc: Peter Zijlstra LKML-Reference: <18981.1900.792795.836858@cargo.ozlabs.ibm.com> Signed-off-by: Ingo Molnar --- kernel/perf_counter.c | 4 ++++ kernel/sched.c | 6 ++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index df319c48c52b..8d2653f137e9 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -3902,8 +3902,12 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) return NOTIFY_OK; } +/* + * This has to have a higher priority than migration_notifier in sched.c. + */ static struct notifier_block __cpuinitdata perf_cpu_nb = { .notifier_call = perf_cpu_notify, + .priority = 20, }; void __init perf_counter_init(void) diff --git a/kernel/sched.c b/kernel/sched.c index ad079f07c9c8..3226cc132e9f 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -7319,8 +7319,10 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu) return NOTIFY_OK; } -/* Register at highest priority so that task migration (migrate_all_tasks) - * happens before everything else. +/* + * Register at high priority so that task migration (migrate_all_tasks) + * happens before everything else. This has to be lower priority than + * the notifier in the perf_counter subsystem, though. */ static struct notifier_block __cpuinitdata migration_notifier = { .notifier_call = migration_call,