From f0e71fcd0fa6f3f5495cd9ad3f1e4acd94446a55 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:09:59 +0530 Subject: zsmalloc: 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 zsmalloc code by using this latter form of callback registration. Cc: Nitin Gupta Cc: Ingo Molnar Signed-off-by: Srivatsa S. Bhat Acked-by: Minchan Kim Signed-off-by: Rafael J. Wysocki --- mm/zsmalloc.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) (limited to 'mm/zsmalloc.c') diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index c03ca5e9fe15..36b4591a7a2d 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -814,21 +814,32 @@ static void zs_exit(void) { int cpu; + cpu_notifier_register_begin(); + for_each_online_cpu(cpu) zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu); - unregister_cpu_notifier(&zs_cpu_nb); + __unregister_cpu_notifier(&zs_cpu_nb); + + cpu_notifier_register_done(); } static int zs_init(void) { int cpu, ret; - register_cpu_notifier(&zs_cpu_nb); + cpu_notifier_register_begin(); + + __register_cpu_notifier(&zs_cpu_nb); for_each_online_cpu(cpu) { ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu); - if (notifier_to_errno(ret)) + if (notifier_to_errno(ret)) { + cpu_notifier_register_done(); goto fail; + } } + + cpu_notifier_register_done(); + return 0; fail: zs_exit(); -- cgit v1.2.3