From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Thomas Pfaff <tpfaff@pcs.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Question about TTY_DO_WRITE_WAKEUP
Date: Thu, 20 Nov 2008 15:55:02 +0000 [thread overview]
Message-ID: <20081120155502.608812d9@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <Pine.LNX.4.64.0811201536150.23073@lxtpfaff.pcs.ditec.de>
> But n_tty_write_wakeup is only called from tty_wakeup when this bit is already
> set, therefore it makes no sense to set this bit in n_tty_write_wakeup again.
The base code should probably really use test_and_clear_bit() when
calling that method.
>
> The flow looks to me as
>
> If the tty driver sets TTY_DO_WRITE_WAKEUP a SIGIO is generated on every
> tty_wakeup.
>
> If it is not set then n_tty_write_wakeup is never called and a SIGIO is not
> generated.
Which isn't perfect (excess SIGIO cases) but doesn't seem incorrect. If
you've not blocked the tty output buffer then write() has not returned a
short write and no SIGIO is due.
Alan
next prev parent reply other threads:[~2008-11-20 15:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-20 10:06 Thomas Pfaff
2008-11-20 13:17 ` Alan Cox
2008-11-20 14:09 ` Thomas Pfaff
2008-11-20 14:31 ` Alan Cox
2008-11-20 15:12 ` Thomas Pfaff
2008-11-20 15:55 ` Alan Cox [this message]
2008-11-20 16:39 ` Thomas Pfaff
2008-11-20 16:47 ` Alan Cox
2008-11-20 16:58 ` Alan Cox
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