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    Subject[PATCH RT 19/25][RFC 3.0.23-rt39-rc1] timer: Fix hotplug for -rt
    From: Steven Rostedt <rostedt@goodmis.org>

    Revert the RT patch:
    Author: Ingo Molnar <mingo@elte.hu>
    Date: Fri Jul 3 08:30:32 2009 -0500
    timers: fix timer hotplug on -rt

    Here we are in the CPU_DEAD notifier, and we must not sleep nor
    enable interrupts.

    There's no problem with sleeping in this notifier.

    But the get_cpu_var() had to be converted to a get_local_var().

    Replace the previous fix with the get_local_var() convert.

    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Cc: Carsten Emde <C.Emde@osadl.org>
    Cc: John Kacur <jkacur@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Clark Williams <clark.williams@gmail.com>
    Cc: stable-rt@vger.kernel.org
    Link: http://lkml.kernel.org/r/20120301190344.948157137@goodmis.org
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    kernel/timer.c | 16 +++++-----------
    1 files changed, 5 insertions(+), 11 deletions(-)

    diff --git a/kernel/timer.c b/kernel/timer.c
    index 937799f..a319c6a 100644
    --- a/kernel/timer.c
    +++ b/kernel/timer.c
    @@ -1743,21 +1743,17 @@ static void __cpuinit migrate_timers(int cpu)
    {
    struct tvec_base *old_base;
    struct tvec_base *new_base;
    - unsigned long flags;
    int i;

    BUG_ON(cpu_online(cpu));
    old_base = per_cpu(tvec_bases, cpu);
    - new_base = get_cpu_var(tvec_bases);
    + new_base = get_local_var(tvec_bases);
    /*
    * The caller is globally serialized and nobody else
    * takes two locks at once, deadlock is not possible.
    */
    - local_irq_save(flags);
    - while (!spin_trylock(&new_base->lock))
    - cpu_relax();
    - while (!spin_trylock(&old_base->lock))
    - cpu_relax();
    + spin_lock_irq(&new_base->lock);
    + spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

    BUG_ON(old_base->running_timer);

    @@ -1771,10 +1767,8 @@ static void __cpuinit migrate_timers(int cpu)
    }

    spin_unlock(&old_base->lock);
    - spin_unlock(&new_base->lock);
    - local_irq_restore(flags);
    -
    - put_cpu_var(tvec_bases);
    + spin_unlock_irq(&new_base->lock);
    + put_local_var(tvec_bases);
    }
    #endif /* CONFIG_HOTPLUG_CPU */

    --
    1.7.8.3



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