From: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> Backport of upstream commit: e30a293e8ad7e6048d6d88bcc114094f964bd67b
https://jira.sw.ru/browse/PSBM-68620 Fixes race between CPU add/del and per-cpu notifier add/del. Below is original commit message: ========================================================================= 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 code in net/core/flow.c by using this latter form of callback registration. Cc: Li RongQing <roy.qing...@gmail.com> Cc: Sasha Levin <sasha.le...@oracle.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Chris Metcalf <cmetc...@tilera.com> Cc: Ingo Molnar <mi...@kernel.org> Acked-by: David S. Miller <da...@davemloft.net> Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> Signed-off-by: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> --- net/core/flow.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/core/flow.c b/net/core/flow.c index e2664a2..20b3ac3 100644 --- a/net/core/flow.c +++ b/net/core/flow.c @@ -450,6 +450,8 @@ int flow_cache_init(struct net *net) if (!fc->percpu) return -ENOMEM; + cpu_notifier_register_begin(); + for_each_online_cpu(i) { if (flow_cache_cpu_prepare(fc, i)) goto err; @@ -457,7 +459,9 @@ int flow_cache_init(struct net *net) fc->hotcpu_notifier = (struct notifier_block){ .notifier_call = flow_cache_cpu, }; - register_hotcpu_notifier(&fc->hotcpu_notifier); + __register_hotcpu_notifier(&fc->hotcpu_notifier); + + cpu_notifier_register_done(); setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd, (unsigned long) fc); @@ -473,6 +477,8 @@ int flow_cache_init(struct net *net) fcp->hash_table = NULL; } + cpu_notifier_register_done(); + free_percpu(fc->percpu); fc->percpu = NULL; _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel