From 576378249c8e0a020aafeaa702c834dff81dd596 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:12:40 +0530 Subject: mm, zswap: 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 zswap code by using this latter form of callback registration. Cc: Ingo Molnar Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- mm/zswap.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'mm/zswap.c') diff --git a/mm/zswap.c b/mm/zswap.c index e55bab9dc41f..d7337fbf6605 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -387,18 +387,18 @@ static int zswap_cpu_init(void) { unsigned long cpu; - get_online_cpus(); + cpu_notifier_register_begin(); for_each_online_cpu(cpu) if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK) goto cleanup; - register_cpu_notifier(&zswap_cpu_notifier_block); - put_online_cpus(); + __register_cpu_notifier(&zswap_cpu_notifier_block); + cpu_notifier_register_done(); return 0; cleanup: for_each_online_cpu(cpu) __zswap_cpu_notifier(CPU_UP_CANCELED, cpu); - put_online_cpus(); + cpu_notifier_register_done(); return -ENOMEM; } -- cgit v1.2.3