[PATCH v3 16/52] x86, cpuid: Fix CPU hotplug callback registration
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STALE4587d
From: Srivatsa S. Bhat <hidden>
Date: 2014-03-10 20:37:04
Also in:
linux-arch, linux-pm, lkml
Subsystem:
cpuid/msr driver, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
"H. Peter Anvin", Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Revision v3 of 3 in this series.
Revisions (3)
- v1 [diff vs current]
- v2 [diff vs current]
- v3 current
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 cpuid code in x86 by using this latter form of callback registration. Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <redacted> Cc: Ingo Molnar <mingo@kernel.org> Cc: x86@kernel.org Signed-off-by: Srivatsa S. Bhat <redacted> --- arch/x86/kernel/cpuid.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 7d9481c..3225ae6c 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c@@ -198,14 +198,15 @@ static int __init cpuid_init(void) goto out_chrdev; } cpuid_class->devnode = cpuid_devnode; - get_online_cpus(); + + cpu_notifier_register_begin(); for_each_online_cpu(i) { err = cpuid_device_create(i); if (err != 0) goto out_class; } - register_hotcpu_notifier(&cpuid_class_cpu_notifier); - put_online_cpus(); + __register_hotcpu_notifier(&cpuid_class_cpu_notifier); + cpu_notifier_register_done(); err = 0; goto out;
@@ -215,7 +216,7 @@ out_class: for_each_online_cpu(i) { cpuid_device_destroy(i); } - put_online_cpus(); + cpu_notifier_register_done(); class_destroy(cpuid_class); out_chrdev: __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
@@ -227,13 +228,13 @@ static void __exit cpuid_exit(void) { int cpu = 0; - get_online_cpus(); + cpu_notifier_register_begin(); for_each_online_cpu(cpu) cpuid_device_destroy(cpu); class_destroy(cpuid_class); __unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid"); - unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); - put_online_cpus(); + __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier); + cpu_notifier_register_done(); } module_init(cpuid_init);