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Date: Fri, 14 Feb 2014 13:26:55 +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, Eddie Wai <eddie.wai@...adcom.com>, "James E.J. Bottomley" <JBottomley@...allels.com>, Ingo Molnar <mingo@...nel.org>, linux-scsi@...r.kernel.org, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> Subject: [PATCH v2 34/52] scsi, bnx2fc: 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 bnx2fc code in scsi by using this latter form of callback registration. Cc: Eddie Wai <eddie.wai@...adcom.com> Cc: "James E.J. Bottomley" <JBottomley@...allels.com> Cc: Ingo Molnar <mingo@...nel.org> Cc: linux-scsi@...r.kernel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com> --- drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c index 9b94850..c4ec235 100644 --- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c +++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c @@ -2586,12 +2586,16 @@ static int __init bnx2fc_mod_init(void) spin_lock_init(&p->fp_work_lock); } + cpu_notifier_register_begin(); + for_each_online_cpu(cpu) { bnx2fc_percpu_thread_create(cpu); } /* Initialize per CPU interrupt thread */ - register_hotcpu_notifier(&bnx2fc_cpu_notifier); + __register_hotcpu_notifier(&bnx2fc_cpu_notifier); + + cpu_notifier_register_done(); cnic_register_driver(CNIC_ULP_FCOE, &bnx2fc_cnic_cb); @@ -2656,13 +2660,17 @@ static void __exit bnx2fc_mod_exit(void) if (l2_thread) kthread_stop(l2_thread); - unregister_hotcpu_notifier(&bnx2fc_cpu_notifier); + cpu_notifier_register_begin(); /* Destroy per cpu threads */ for_each_online_cpu(cpu) { bnx2fc_percpu_thread_destroy(cpu); } + __unregister_hotcpu_notifier(&bnx2fc_cpu_notifier); + + cpu_notifier_register_done(); + destroy_workqueue(bnx2fc_wq); /* * detach from scsi transport -- 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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