Date: Wed, 12 Nov 1997 13:45:38 +0900 From: Kenjiro Cho <kjc@csl.sony.co.jp> To: Antonio Luis Alves <aalves@dei.uc.pt> Cc: freebsd-atm@FreeBSD.ORG Subject: Re: ATM driver & udp stream Message-ID: <199711120445.NAA24120@hotaka.csl.sony.co.jp> In-Reply-To: Your message of "Wed, 12 Nov 1997 03:06:46 GMT." <Pine.BSF.3.96.971112005854.20573A-100000@zorg.dei.uc.pt>
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>> All was working well until I made a UDP stream test. The sender was a >> Pentium 233mmx and on the receive side a Pentium 166. The test is a normal >> netperf UDP_STREAM with default values for the datagram, which is the max >> udp datagram 9216. The driver crashes at the pdu receive routine when >> accessing the segments which form the pdu. With the debugger I can see that >> the mbuf handles are correct but the data on the mbuf is not. Some times >> the m_type is MT_FREE and m->next as got a valid pointer on it, and other >> times all the members of the mbuf are zero. On a normal situation the >> mbufs would be of type MT_DATA, and correctly initialized with the >> pointers to the external free and reference function, m_len, ext_size and >> ext_buffer. >> From the firmware guide it says the card never touches the mbuf, it just >> pass the mbuf handle received from the supply routine to the segments on >> the received pdu descriptor. It sounds familiar to me..., so you might want to take a look at the following possibility. I had a similar experience with Chuck Cranor's ATM driver long time ago. It turns out that, under heavy load, a circular list holding pointers to mbufs gets completely full and wrapped around. As a result, a wrong mbuf in use gets freed. The system crashes after a while when it refers to the misplaced mbuf. IMO, it's a very bad idea to put a free list chain at the top of a mbuf cluster data area when a mbuf is on the free list. It is very hard to debug if something goes wrong. --kj
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