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SubjectRe: more signal locking bugs?
Linus Torvalds wrote:

>In short, everything really seems to be pointing that way: the current
>task lock simply _is_ broken, and has apparently always been broken (but
>the ABBA deadlock is just extremely rare in practice, since you have to
>get an interrupt at just the right point on one CPU, while you have the AB
>case on another).\
>
ABBA is not a deadlock, because linux read_locks permit recursive calls.

read_lock(tasklist_lock);
task_lock(tsk);
read_lock(tasklist_lock);

Does not deadlock, nor any other ordering.

The tasklist_lock is never taken for write from bh or irq context.

--
Manfred

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