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authorSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>2014-03-11 02:12:08 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-03-20 13:43:48 +0100
commitc270a817196a9374a2dc730624d1501dced40b4d (patch)
tree27de495f536c14bb1844dee4b825c5c7a8a056eb /kernel
parentd39ad278a3001c860da4d7c13e51259b1904bec5 (diff)
downloadop-kernel-dev-c270a817196a9374a2dc730624d1501dced40b4d.zip
op-kernel-dev-c270a817196a9374a2dc730624d1501dced40b4d.tar.gz
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 <viro@zeniv.linux.org.uk> Cc: Mauro Carvalho Chehab <mchehab@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/profile.c20
1 files changed, 15 insertions, 5 deletions
diff --git a/kernel/profile.c b/kernel/profile.c
index ebdd9c1..93b2a3f 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 */
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