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    SubjectRe: more signal locking bugs?
    Linus Torvalds wrote:

    >>What about this minimal patch? The performance critical operation is
    >>signal delivery - we should fix the synchronization between signal
    >>delivery and exec first.
    >>
    >>
    >
    >The patch looks ok, although I'd also remove the locking and testing from
    >collect_sigign_sigcatch() once it is done at a higher level.
    >
    >And yeah, what about signal delivery? Put back the same lock there?
    >
    >
    I don't know.
    Taking read_lock(&tasklist_lock) for send_specific_sig_info might hurt
    scalability. Ingo?

    If we do not want a global lock, then we have two options:
    - make task_lock an interrupt spinlock.
    - add a second spinlock to the task structure, for the signal stuff.

    Design question - what's worse? Memory bloat or a few additional
    local_irq_{en,dis}able().
    I don't care - no performance critical codepaths.
    Additionally many task_lock()/task_unlock users could be replaced with
    spin_unlock_wait(&task->alloc_lock), which would not need the
    local_irq_disable().

    --
    Manfred

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