Messages in this thread | | | Date | Wed, 21 Jun 2006 18:15:13 -0300 | From | "Luiz Fernando N. Capitulino" <> | Subject | Re: Serial-Core: USB-Serial port current issues. |
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On Wed, 21 Jun 2006 17:43:36 +0100 Russell King <rmk+lkml@arm.linux.org.uk> wrote:
| In the uart_update_mctrl() case, the purpose of the locking is to | prevent two concurrent changes to the modem control state resulting | in an inconsistency between the hardware and the software state. If | it's provable that it is always called from process context (and | it isn't called from a lock_kernel()-section or the lock_kernel() | section doesn't mind a rescheduling point being introduced there), | there's no problem converting that to a mutex.
Ok, then I can submit my debug patch to answer these questions.
might_sleep() can catch the lock_kernel()-section case right?
| With get_mctrl(), the situation is slightly more complicated, because | we need to atomically update tty->hw_stopped in some circumstances | (that may also be modified from irq context.) Therefore, to give | the driver a consistent locking picture, the spinlock is _always_ | held.
Is it too bad (wrong?) to only protect the tty->hw_stopped update by the spinlock? Then the call to get_mctrl() could be protected by a mutex, or is it messy?
-- Luiz Fernando N. Capitulino - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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