From owner-freebsd-current  Wed May  2 19: 9:54 2001
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Date: Wed, 2 May 2001 21:09:39 -0500 (CDT)
From: Jonathan Lemon <jlemon@flugsvamp.com>
Message-Id: <200105030209.f4329dR74591@prism.flugsvamp.com>
To: tlambert@primenet.com, current@freebsd.org
Subject: Re: panic in fxp driver
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In-Reply-To: <local.mail.freebsd-current/200105030158.SAA29983@usr09.primenet.com>
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In article <local.mail.freebsd-current/200105030158.SAA29983@usr09.primenet.com> you write:
>The fxp driver is broken in a lot of places.
>
>For example, in fxp_intr():
>
>                        for (txp = sc->cbl_first; sc->tx_queued &&
>                            (txp->cb_status & FXP_CB_STATUS_C) != 0;
>                            txp = txp->next) {
>                                if (txp->mb_head != NULL) {
>                                        m_freem(txp->mb_head);
>                                        txp->mb_head = NULL;
>                                }
>                                sc->tx_queued--;
>                        }
>
>...notice the "for" loop doesn't check to see if "txp = txp->next"
>ends up being NULL?  You can get this, if you put your system
>under extreme load.

I would be quite interested in knowing just how you manage
to accomplish that, given that all the transmit control buffers
are arranged in a circular linked list:

    fxp_init(void *xsc)
    {
	    ...
	    for (i = 0; i < FXP_NTXCB; i++) {
		    ...
		    txp[i].next = &txp[(i + 1) & FXP_TXCB_MASK];
	    }


I would suggest actually examining the rest of the code to see
how it works before making erroneous proclamations based on the 
myopic examination of a single statement.
--
Jonathan

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