Re: hci_ldsic nested locking problem

[Alan Cox]

On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> Hi,
> 
> when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> tty->ops->write() to actually send the characters, but that call will
> try to acquire the same port lock again.
> 
> Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> Am I correct to assume that ->write_wakeup() is supposed to *just*
> wakeup the bottom half so we handle ->write() in another context ?
> 
> Is it legal to call tty->ops->write() from within ->write_wakeup() ?

It isn't because you might send all the bytes and go

	write
		write_wakeup
			write
				write wakeup
					...

and recurse

Alan


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