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Date: Fri, 14 Feb 2014 13:30:18 +0530 From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> To: paulus@...ba.org, oleg@...hat.com, mingo@...nel.org, rusty@...tcorp.com.au, peterz@...radead.org, tglx@...utronix.de, akpm@...ux-foundation.org Cc: paulmck@...ux.vnet.ibm.com, tj@...nel.org, walken@...gle.com, ego@...ux.vnet.ibm.com, linux@....linux.org.uk, rjw@...ysocki.net, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com, Andrew Morton <akpm@...ux-foundation.org>, Rik van Riel <riel@...hat.com>, Johannes Weiner <hannes@...xchg.org>, Cody P Schafer <cody@...ux.vnet.ibm.com>, Toshi Kani <toshi.kani@...com>, Dave Hansen <dave@...1.net>, Ingo Molnar <mingo@...nel.org>, linux-mm@...ck.org, Christoph Lameter <cl@...ux.com>, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> Subject: [PATCH v2 49/52] mm, vmstat: 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 vmstat code in the MM subsystem by using this latter form of callback registration. Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Rik van Riel <riel@...hat.com> Cc: Johannes Weiner <hannes@...xchg.org> Cc: Cody P Schafer <cody@...ux.vnet.ibm.com> Cc: Toshi Kani <toshi.kani@...com> Cc: Dave Hansen <dave@...1.net> Cc: Ingo Molnar <mingo@...nel.org> Cc: linux-mm@...ck.org Acked-by: Christoph Lameter <cl@...ux.com> Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com> --- mm/vmstat.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index 7249614..12a553e 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1290,14 +1290,14 @@ static int __init setup_vmstat(void) #ifdef CONFIG_SMP int cpu; - register_cpu_notifier(&vmstat_notifier); + cpu_notifier_register_begin(); + __register_cpu_notifier(&vmstat_notifier); - get_online_cpus(); for_each_online_cpu(cpu) { start_cpu_timer(cpu); node_set_state(cpu_to_node(cpu), N_CPU); } - put_online_cpus(); + cpu_notifier_register_done(); #endif #ifdef CONFIG_PROC_FS proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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