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    SubjectRe: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes.
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    On Wed, 2011-01-26 at 13:17 +0530, Srikar Dronamraju wrote:
    > * Peter Zijlstra <peterz@infradead.org> [2011-01-25 13:15:45]:
    >
    > > > +
    > > > + if (atomic_read(&uprobe->ref) == 1) {
    > > > + synchronize_sched();
    > > > + rb_erase(&uprobe->rb_node, &uprobes_tree);
    > >
    > > How is that safe without holding the treelock?
    >
    > Right,
    > Something like this should be good enuf right?
    >
    > if (atomic_read(&uprobe->ref) == 1) {
    > synchronize_sched();
    > spin_lock_irqsave(&treelock, flags);
    > rb_erase(&uprobe->rb_node, &uprobes_tree);
    > spin_lock_irqrestore(&treelock, flags);
    > iput(uprobe->inode);
    > }
    >

    How is the atomic_read() not racy with a future increment, and what is
    that synchronize_sched() thing for?


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