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Message-ID: <20110420163535.77b5826f@lxorguk.ukuu.org.uk> Date: Wed, 20 Apr 2011 16:35:35 +0100 From: Alan Cox <alan@...rguk.ukuu.org.uk> To: John Linn <John.Linn@...inx.com> Cc: <linux-kernel@...r.kernel.org>, <linux-serial@...r.kernel.org> Subject: Re: [PATCH] tty/serial: add support for Xilinx PS UART > I see the subtle locking issue you mention. > > This looks like a good way to help it, but it's not clear to me what to > do in an isr > if the function returns a NULL for the tty. In other places you can say > the tty It can happen, you must deal with it. > It seems easier in this case to just move the tty = > port->state->port.tty to after > the lock is acquired. It can still be NULL. > I'm sure there's something obvious I'm missing here. It varies what drivers do but essentially what has occurred is that the user side of the tty has gone away and you have an IRQ still. Your port is still around as the lifetime of the port is the lifetime of your serial driver creating/deleting it, but your tty has gone. In those cases you need to do whatever needs doing to handle the IRQ and processing that doesn't require the tty. That varies by device, in many cases for example you read the data and chuck it rather than stuffing it into the flip buffer. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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