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    Subject[PATCH] I/OAT: remove CPU hotplug lock from net_dma_rebalance
    Remove the lock_cpu_hotplug()/unlock_cpu_hotplug() calls from net_dma_rebalance

    The lock_cpu_hotplug()/unlock_cpu_hotplug() sequence in net_dma_rebalance
    is both incorrect (as pointed out by David Miller) because lock_cpu_hotplug()
    may sleep while the net_dma_event_lock spinlock is held, and unnecessary (as
    pointed out by Andrew Morton) as spin_lock() disables preemption which
    protects from CPU hotplug events.

    Signed-off-by: Chris Leech <christopher.leech@intel.com>
    ---

    net/core/dev.c | 5 -----
    1 files changed, 0 insertions(+), 5 deletions(-)

    diff --git a/net/core/dev.c b/net/core/dev.c
    index 4d2b516..780d770 100644
    --- a/net/core/dev.c
    +++ b/net/core/dev.c
    @@ -3429,12 +3429,9 @@ static void net_dma_rebalance(void)
    unsigned int cpu, i, n;
    struct dma_chan *chan;

    - lock_cpu_hotplug();
    -
    if (net_dma_count == 0) {
    for_each_online_cpu(cpu)

    rcu_assign_pointer(per_cpu(softnet_data.net_dma, cpu), NULL);
    - unlock_cpu_hotplug();
    return;
    }

    @@ -3454,8 +3451,6 @@ static void net_dma_rebalance(void)
    i++;
    }
    rcu_read_unlock();
    -
    - unlock_cpu_hotplug();
    }

    /**
    -
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