hci_ldsic nested locking problem

From: Felipe Balbi
Date: Thu Mar 20 2014 - 12:36:39 EST


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() ?

cheers

--
balbi

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