The commit is pushed to "branch-rh7-3.10.0-514.26.1.vz7.33.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-514.26.1.vz7.33.10
------>
commit 2d7d7eb08268527613f2b3d54b9c388159305199
Author: Srivatsa S. Bhat <[email protected]>
Date: Tue Jul 18 18:20:27 2017 +0400
ms/net/core/flow.c: Fix CPU hotplug callback registration
Backport of upstream commit: e30a293e8ad7e6048d6d88bcc114094f964bd67b
https://jira.sw.ru/browse/PSBM-68620
Fixes race between CPU add/del and per-cpu notifier add/del.
Signed-off-by: Stanislav Kinsburskiy <[email protected]>
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 <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Ingo Molnar <[email protected]>
Acked-by: David S. Miller <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>
---
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;
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