linux-kernel - RE: [REGRESSION] 2.6.24-rc7: e1000: Detected Tx Unit Hang

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Date:	Tue, 15 Jan 2008 13:53:43 -0800
From:	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
To:	<slavon@...telecom.ru>, "Frans Pop" <elendil@...net.nl>
Cc:	"David Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [REGRESSION] 2.6.24-rc7: e1000: Detected Tx Unit Hang

slavon@...telecom.ru wrote:
> Quoting Frans Pop <elendil@...net.nl>:
>>> (Note this isn't the final correct patch we should apply.  There  is
>>> no reason why this revert back to the older ->poll() logic  here
>>> should have any effect on the TX hang triggering...)
>> 
>> s/no reason/no obvious reason/ ? ;-)

The tx code has an "early exit" that tries to limit the amount of tx
packets handled in a single poll loop and requires napi or interrupt
rescheduling based on the return value from e1000_clean_tx_irq.

see this code in e1000_clean_tx_irq

4005 #ifdef CONFIG_E1000_NAPI
4006 #define E1000_TX_WEIGHT 64
4007 >       >       /* weight of a sort for tx, to avoid endless
transmit cleanup */
4008 >       >       if (count++ == E1000_TX_WEIGHT) break;
4009 #endif

I think that is probably related.  For a test you could apply the
original patch, and remove this "break" just by commenting out line
4008.  This would guarantee all tx work is cleaned at every e1000_clean

Jesse
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