perf_counter: initialize the per-cpu context earlier

percpu scheduling for perfcounters wants to take the context lock,
but that lock first needs to be initialized. Currently it is an
early_initcall() - but that is too late, the task tick runs much
sooner than that.

Call it explicitly from the scheduler init sequence instead.

[ Impact: fix access-before-init crash ]

LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index f776851f8c4b1632d615b7457eda36e22b27cadf..a356fa69796c59650d62d2f8ad4bf88145e51009 100644 (file)
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -573,6 +573,8 @@ extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
 
 extern int sysctl_perf_counter_priv;
 
+extern void perf_counter_init(void);
+
 #else
 static inline void
 perf_counter_task_sched_in(struct task_struct *task, int cpu)          { }
@@ -600,9 +602,10 @@ perf_counter_mmap(unsigned long addr, unsigned long len,
 
 static inline void
 perf_counter_munmap(unsigned long addr, unsigned long len,
-                   unsigned long pgoff, struct file *file)             { }
+                   unsigned long pgoff, struct file *file)             { }
 
 static inline void perf_counter_comm(struct task_struct *tsk)          { }
+static inline void perf_counter_init(void)                             { }
 #endif
 
 #endif /* __KERNEL__ */

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index b9679c36bcc281e38236e57e7661dc53efe4fe38..fcdafa234a5d9626d28d32a5db50494b2222b2f1 100644 (file)
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3265,15 +3265,12 @@ static struct notifier_block __cpuinitdata perf_cpu_nb = {
        .notifier_call          = perf_cpu_notify,
 };
 
-static int __init perf_counter_init(void)
+void __init perf_counter_init(void)
 {
        perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_UP_PREPARE,
                        (void *)(long)smp_processor_id());
        register_cpu_notifier(&perf_cpu_nb);
-
-       return 0;
 }
-early_initcall(perf_counter_init);
 
 static ssize_t perf_show_reserve_percpu(struct sysdev_class *class, char *buf)
 {

diff --git a/kernel/sched.c b/kernel/sched.c
index 2f600e30dcf0581d8fbbf73c0b1ec14f81cb2711..a728976a3a6c914da36aeca990a4b7658ea60ebd 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -39,6 +39,7 @@
 #include <linux/completion.h>
 #include <linux/kernel_stat.h>
 #include <linux/debug_locks.h>
+#include <linux/perf_counter.h>
 #include <linux/security.h>
 #include <linux/notifier.h>
 #include <linux/profile.h>
@@ -8996,7 +8997,7 @@ void __init sched_init(void)
                 * 1024) and two child groups A0 and A1 (of weight 1024 each),
                 * then A0's share of the cpu resource is:
                 *
-                *      A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
+                *      A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
                 *
                 * We achieve this by letting init_task_group's tasks sit
                 * directly in rq->cfs (i.e init_task_group->se[] = NULL).
@@ -9097,6 +9098,8 @@ void __init sched_init(void)
        alloc_bootmem_cpumask_var(&cpu_isolated_map);
 #endif /* SMP */
 
+       perf_counter_init();
+
        scheduler_running = 1;
 }