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    SubjectRe: [PATCH] RT: Checks for cmpxchg in get_task_struct_rcu()
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    Date

    Checks for cmpxchg in get_task_struct_rcu() . No race version.

    Signed-Off-By: Daniel Walker <dwalker@mvista.com>

    Index: linux-2.6.13/include/linux/sched.h
    ===================================================================
    --- linux-2.6.13.orig/include/linux/sched.h
    +++ linux-2.6.13/include/linux/sched.h
    @@ -1026,13 +1026,24 @@ static inline int get_task_struct_rcu(st
    {
    int oldusage;

    +#ifdef __HAVE_ARCH_CMPXCHG
    do {
    oldusage = atomic_read(&t->usage);
    if (oldusage == 0) {
    return 0;
    }
    } while (cmpxchg(&t->usage.counter,
    - oldusage, oldusage + 1) != oldusage);
    + oldusage, oldusage + 1) != oldusage);
    +#else
    + raw_local_irq_disable();
    + oldusage = atomic_read(&t->usage);
    + if (oldusage == 0) {
    + raw_local_irq_enable();
    + return 0;
    + }
    + atomic_inc(&t->usage);
    + raw_local_irq_enable();
    +#endif
    return 1;
    }


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