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From: Bill Paul <wpaul@FreeBSD.ORG>
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	Sun, 6 Sep 1998 07:58:47 -0700 (PDT)
Date: Sun, 6 Sep 1998 07:58:47 -0700 (PDT)
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To: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG
Subject: cvs commit: src/sys/pci if_xl.c
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wpaul       1998/09/06 07:58:47 PDT

  Modified files:
    sys/pci              if_xl.c 
  Log:
  Patch the transmit error handler to avoid following NULL pointers and
  generating a trap 12 panic. The code blindly assumed that in the event
  of a transmit error, the packet that caused the error would still be
  at the head of the driver's transmit queue (sc->xl_cdata.xl_tx_head).
  However in the case of error 82 (which indicates that a transmit error
  occurred after part of the transmit FIFO memory has been reclaimed)
  this is not true: the TX queue has already been flushed, and the
  pointer to the head of the queue is NULL, so trying to dereference
  the pointer to find the transmit descriptor address causes a crash.
  
  The code now checks for a NULL pointer before trying to reload the
  chip's download pointer register. There may still be error messages
  printed warning of the transmit error, but no panic should occur.
  
  Note that this eror code is only generated with "cyclone" chipsets
  (3c900B, 3c905B, and presumeably the 3c980 server adapter). It should
  only appear during periods of heavy traffic, probably only on
  non-switched networks.
  
  Problem reported by: Darcy Buskermolen <darcy@ok-connect.com>
  
  Revision  Changes    Path
  1.10      +4 -3      src/sys/pci/if_xl.c