From c270a817196a9374a2dc730624d1501dced40b4d Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:12:08 +0530 Subject: profile: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the profile code by using this latter form of callback registration. Cc: Al Viro Cc: Mauro Carvalho Chehab Cc: Ingo Molnar Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- kernel/profile.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) (limited to 'kernel/profile.c') diff --git a/kernel/profile.c b/kernel/profile.c index ebdd9c1a86b4..93b2a3fe0a64 100644 --- a/kernel/profile.c +++ b/kernel/profile.c @@ -591,18 +591,28 @@ out_cleanup: int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */ { struct proc_dir_entry *entry; + int err = 0; if (!prof_on) return 0; - if (create_hash_tables()) - return -ENOMEM; + + cpu_notifier_register_begin(); + + if (create_hash_tables()) { + err = -ENOMEM; + goto out; + } + entry = proc_create("profile", S_IWUSR | S_IRUGO, NULL, &proc_profile_operations); if (!entry) - return 0; + goto out; proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t)); - hotcpu_notifier(profile_cpu_callback, 0); - return 0; + __hotcpu_notifier(profile_cpu_callback, 0); + +out: + cpu_notifier_register_done(); + return err; } module_init(create_proc_profile); #endif /* CONFIG_PROC_FS */ -- cgit