| Message ID | 20140205221345.19080.20784.stgit@srivatsabhat.in.ibm.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> Date: Thu, 06 Feb 2014 03:43:46 +0530 > 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: ... > 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: ... > Fix the code in net/core/flow.c by using this latter form of callback > registration. > > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Li RongQing <roy.qing.li@gmail.com> > Cc: Sasha Levin <sasha.levin@oracle.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Chris Metcalf <cmetcalf@tilera.com> > Cc: netdev@vger.kernel.org > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: David Miller <davem@davemloft.net> Date: Thu, 06 Feb 2014 20:39:21 -0800 (PST) > From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> > Date: Thu, 06 Feb 2014 03:43:46 +0530 > >> 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: > ... >> 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: > ... >> Fix the code in net/core/flow.c by using this latter form of callback >> registration. >> >> Cc: "David S. Miller" <davem@davemloft.net> >> Cc: Li RongQing <roy.qing.li@gmail.com> >> Cc: Sasha Levin <sasha.levin@oracle.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Chris Metcalf <cmetcalf@tilera.com> >> Cc: netdev@vger.kernel.org >> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > > Applied. I just realized that this has a dependency not in the 'net' tree, so I reverted and assume you will merge this with the patch that provides the necessary interface(s). Signed-off-by: David S. Miller <davem@davemloft.net> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/core/flow.c b/net/core/flow.c index dfa602c..0f2c995 100644 --- a/net/core/flow.c +++ b/net/core/flow.c @@ -456,6 +456,8 @@ static int __init flow_cache_init(struct flow_cache *fc) if (!fc->percpu) return -ENOMEM; + cpu_maps_update_begin(); + for_each_online_cpu(i) { if (flow_cache_cpu_prepare(fc, i)) goto err; @@ -463,7 +465,9 @@ static int __init flow_cache_init(struct flow_cache *fc) fc->hotcpu_notifier = (struct notifier_block){ .notifier_call = flow_cache_cpu, }; - register_hotcpu_notifier(&fc->hotcpu_notifier); + __register_hotcpu_notifier(&fc->hotcpu_notifier); + + cpu_maps_update_done(); setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd, (unsigned long) fc); @@ -479,6 +483,8 @@ err: fcp->hash_table = NULL; } + cpu_maps_update_done(); + free_percpu(fc->percpu); fc->percpu = NULL;
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_maps_update_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_maps_update_done(); Fix the code in net/core/flow.c by using this latter form of callback registration. Cc: "David S. Miller" <davem@davemloft.net> Cc: Li RongQing <roy.qing.li@gmail.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: netdev@vger.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- net/core/flow.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html