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    Subject[tip:irq/urgent] irq: Ensure irq_exit() code runs with interrupts disabled
    Commit-ID:  630e7580f681475d92d87e78373e4136096e12f2
    Gitweb: http://git.kernel.org/tip/630e7580f681475d92d87e78373e4136096e12f2
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Wed, 20 Feb 2013 22:00:48 +0100
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Thu, 21 Feb 2013 18:32:44 +0100

    irq: Ensure irq_exit() code runs with interrupts disabled

    We had already a few problems with code called from irq_exit() when
    interrupted from a nesting interrupt. This can happen on architectures
    which do not define __ARCH_IRQ_EXIT_IRQS_DISABLED.

    __ARCH_IRQ_EXIT_IRQS_DISABLED should go away and we want to make it
    mandatory to call irq_exit() with interrupts disabled.

    As a temporary protection disable interrupts for those architectures
    which do not define __ARCH_IRQ_EXIT_IRQS_DISABLED and add a WARN_ONCE
    when an architecture which defines __ARCH_IRQ_EXIT_IRQS_DISABLED calls
    irq_exit() with interrupts enabled.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Linus Torvalds <torvalds@linuxfoundation.org>
    Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1302202155320.22263@ionos

    ---
    kernel/softirq.c | 11 +++++++++++
    1 file changed, 11 insertions(+)

    diff --git a/kernel/softirq.c b/kernel/softirq.c
    index f5cc25f..d1f7943 100644
    --- a/kernel/softirq.c
    +++ b/kernel/softirq.c
    @@ -341,6 +341,14 @@ static inline void invoke_softirq(void)
    */
    void irq_exit(void)
    {
    +#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
    + unsigned long flags;
    +
    + local_irq_save(flags);
    +#else
    + WARN_ON_ONCE(!irqs_disabled();
    +#endif
    +
    account_irq_exit_time(current);
    trace_hardirq_exit();
    sub_preempt_count(IRQ_EXIT_OFFSET);
    @@ -354,6 +362,9 @@ void irq_exit(void)
    #endif
    rcu_irq_exit();
    sched_preempt_enable_no_resched();
    +#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
    + local_irq_restore(flags);
    +#endif
    }

    /*

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