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Altera_Forum's avatar
Altera_Forum
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19 years ago

Delayed ethernet packet processing (bug?)

As reported to bugzilla:

If the priority of the ethernet driver thread is lower (higher# ) than the FreeBSD Network Thread, then the Network Thread can get prematurely woken up to process an incoming ethernet pkt before the packet is fully enqued. Specifically:

if_ethersubr:ether_demux() calls schednetisr() (which wakes up network thread) prior to the pkt being enqued with that call to IF_ENQUEUE().

This might not be obvious because a subsequent incoming packet can (partially) process the queue.

One solution is to make sure the thread priority of the ethernet driver Handler_RxEvent() is higher (lower# ) than the FreeBSD Network Thread (default 7). A kludge option is to call both:

schednetisr(2/*or NETISR_IP*/);

schednetisr(18/* or NETISR_ARP*/);

after each recv packet is processed by the Handler_RxEvent() call.

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    19 years ago

    Actually, this seems to be a problem if any network thread calling select(), such as tftp and probably most others, are at a lower priority (higher# ) than the FreeBSD Network Thread.