AcoSail/kernel_optimize_test
8
0
Fork 0
forked from luck/tmp_suning_uos_patched
Code Pull Requests Activity

powercap, intel-rapl: Fix CPU hotplug callback registration

Browse Source 
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 intel-rapl code in the powercap driver by using this latter form
of callback registration. But retain the calls to get/put_online_cpus(),
since they also protect the function rapl_cleanup_data(). By nesting
get/put_online_cpus() *inside* cpu_notifier_register_begin/done(), we avoid
the ABBA deadlock possibility mentioned above.

Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Tested-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Srivatsa S. Bhat 2014-03-11 02:09:26 +05:30 committed by Rafael J. Wysocki
parent 4b0b68af37
commit 009f225ef0
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/powercap/intel_rapl.c
View File

@ -1369,6 +1369,9 @@ static int __init rapl_init(void)
return -ENODEV;
}
cpu_notifier_register_begin();
/* prevent CPU hotplug during detection */
get_online_cpus();
ret = rapl_detect_topology();
@ -1380,20 +1383,23 @@ static int __init rapl_init(void)
ret = -ENODEV;
goto done;
}
register_hotcpu_notifier(&rapl_cpu_notifier);
__register_hotcpu_notifier(&rapl_cpu_notifier);
done:
put_online_cpus();
cpu_notifier_register_done();
return ret;
}
static void __exit rapl_exit(void)
{
cpu_notifier_register_begin();
get_online_cpus();
unregister_hotcpu_notifier(&rapl_cpu_notifier);
__unregister_hotcpu_notifier(&rapl_cpu_notifier);
rapl_unregister_powercap();
rapl_cleanup_data();
put_online_cpus();
cpu_notifier_register_done();
}
module_init(rapl_init);