From: Denis Joseph Barrow <D.Barow@option•com>
To: Alan Cox <alan@lxorguk•ukuu.org.uk>
Cc: Linux USB kernel mailing list <linux-usb@vger•kernel.org>,
Linux netdev Mailing list <netdev@vger•kernel.org>,
Paul Hardwick <P.Hardwick@option•com>
Subject: re your change to the low_latency flag in the hso driver in 2.6.29-rc1
Date: Mon, 12 Jan 2009 18:23:53 +0100 [thread overview]
Message-ID: <496B7CA9.6080403@option.com> (raw)
Hi Alan,
I remember removing the low_latency flag to 0 once & if I recall correctly performance
was severely impacted & there may have been other problems which I don't recall.
even worse I believe the code can now hang the kernel, the fix is simple, in
put_rxbuf_data I'm dependent on the TTY_THROTTLED bit to exit the loop.
Now tty_insert_flip_string can return 0 bytes leading to an infinite loop if tty buffers are full,
as write_length_remaining never goes to zero as I am dependent on the line
discipline being called from tty_flip_buffer_push to set TTY_THROTTLED by calling flush_to_ldisc
checking if curr_write_len=0 from tty_insert_flip_string might fix the problem
Please look at put_rxbuf_data carefully, there might be other gremlins. The serial port
is supposed to be high performance this fix will impact this
--
best regards,
D.J. Barrow
Linux Kernel Developer
Option NV, Gaston Geenslaan 14, 3001 Leuven, Belgium
T: +32 16 311 621
F: +32 16 207 164
d.barow@option•com
www.option.com
Disclaimer:
http://www.option.com/company/disclaimer.shtml
next reply other threads:[~2009-01-12 17:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-12 17:23 Denis Joseph Barrow [this message]
[not found] ` <496B7CA9.6080403-x9gZzRpC1QbQT0dZR+AlfA@public.gmane.org>
2009-01-12 17:45 ` re your change to the low_latency flag in the hso driver in 2.6.29-rc1 Alan Cox
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