> while switching current->sighand de_thread does:
>
> write_lock_irq(&tasklist_lock);
> spin_lock(&oldsighand->siglock);
> spin_lock(&newsighand->siglock);
>
> current->sighand = newsighand;
> recalc_sigpending();
>
> Is these 2 sighand locks are really needed?
Yes. Other processes can do spin_lock_irq(&ourtask->sighand->siglock);
without holding tasklist_lock. If someone just did that, they hold
oldsighand->siglock but no newsighand->siglock, and may then be about to
look at ourtask->sighand. By holding oldsighand->siglock, we ensure that
we can't be colliding with anything like that.
> The only possibility that I can imagine is that some process
> does:
> read_lock(tasklist_lock);
> task = find_task();
> spin_lock(task->sighand->siglock);
> read_unlock(tasklist_lock);
> play with task->signal
>
> Is this possible/allowed?
Yes.
> Signed-off-by: Oleg Nesterov <[email protected]>
NAK from me.
Thanks,
Roland
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
