Date: Mon, 29 Mar 2004 11:33:21 +0100
From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.6.5-rc2-mm5
Message-ID: <20040329113321.A23135@flint.arm.linux.org.uk>
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	linux-kernel@vger.kernel.org
References: <20040329014525.29a09cc6.akpm@osdl.org> <20040329105729.A20272@flint.arm.linux.org.uk> <20040329022556.255c71bb.akpm@osdl.org>
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In-Reply-To: <20040329022556.255c71bb.akpm@osdl.org>; from akpm@osdl.org on Mon, Mar 29, 2004 at 02:25:56AM -0800
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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.

-- 
Russell King
 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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