Once stop_machine() is gone from the CPU offline path, we won't be able to
depend on preempt_disable() or local_irq_disable() to prevent CPUs from
going offline from under us.

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
while invoking from atomic context.

Cc: Robert Love <robert.w.l...@intel.com>
Cc: "James E.J. Bottomley" <jbottom...@parallels.com>
Cc: de...@open-fcoe.org
Cc: linux-s...@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com>
---

 drivers/scsi/fcoe/fcoe.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index 666b7ac..c971a17 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -1475,6 +1475,7 @@ static int fcoe_rcv(struct sk_buff *skb, struct 
net_device *netdev,
         * was originated, otherwise select cpu using rx exchange id
         * or fcoe_select_cpu().
         */
+       get_online_cpus_atomic();
        if (ntoh24(fh->fh_f_ctl) & FC_FC_EX_CTX)
                cpu = ntohs(fh->fh_ox_id) & fc_cpu_mask;
        else {
@@ -1484,8 +1485,10 @@ static int fcoe_rcv(struct sk_buff *skb, struct 
net_device *netdev,
                        cpu = ntohs(fh->fh_rx_id) & fc_cpu_mask;
        }
 
-       if (cpu >= nr_cpu_ids)
+       if (cpu >= nr_cpu_ids) {
+               put_online_cpus_atomic();
                goto err;
+       }
 
        fps = &per_cpu(fcoe_percpu, cpu);
        spin_lock(&fps->fcoe_rx_list.lock);
@@ -1505,6 +1508,7 @@ static int fcoe_rcv(struct sk_buff *skb, struct 
net_device *netdev,
                spin_lock(&fps->fcoe_rx_list.lock);
                if (!fps->thread) {
                        spin_unlock(&fps->fcoe_rx_list.lock);
+                       put_online_cpus_atomic();
                        goto err;
                }
        }
@@ -1526,6 +1530,7 @@ static int fcoe_rcv(struct sk_buff *skb, struct 
net_device *netdev,
        if (fps->thread->state == TASK_INTERRUPTIBLE)
                wake_up_process(fps->thread);
        spin_unlock(&fps->fcoe_rx_list.lock);
+       put_online_cpus_atomic();
 
        return 0;
 err:

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