From: Russell King
Date: Mon Mar 29 2004 - 05:34:19 EST
On Mon, Mar 29, 2004 at 02:25:56AM -0800, Andrew Morton wrote:
> > and it is completely valid for ->close to be called while
> > another thread is in ->open. In fact, it's desirable since ->open may
> > be waiting for the DCD line from a modem to activate, while there may
> > be a simultaneous O_NONBLOCK open/ioctl/close from stty.
> ->open is not called under tty_sem. With this change, ->close is called
> under tty_sem.
> Are ->close implementations likely to block on hardware events?
Historically they have blocked in a well defined manner - eg when
dropping the DTR signal for a specified minimum time period.
They can also block until the data awaiting transmission has been
sent, which by default has a 30 second timeout, or may be configured
to be "until sent". Of course, if CTS is deasserted, we will wait
until the timeout.
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
2.6 Serial core
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