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Re: LLTX and netif_stop_queue

To: hadi@xxxxxxxxxx
Subject: Re: LLTX and netif_stop_queue
From: Roland Dreier <roland@xxxxxxxxxxx>
Date: Sun, 19 Dec 2004 14:35:26 -0800
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxx, openib-general@xxxxxxxxxx
In-reply-to: <1103484675.1050.158.camel@jzny.localdomain> (jamal's message of "19 Dec 2004 14:31:15 -0500")
References: <52llbwoaej.fsf@topspin.com> <20041217214432.07b7b21e.davem@davemloft.net> <1103484675.1050.158.camel@jzny.localdomain>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Security Through Obscurity, linux)
    jamal> How about releasing the qlock only when the LLTX transmit
    jamal> lock is grabbed? That should bring it to par with what it
    jamal> was originally.

This seems a little risky.  I can't point to a specific deadlock but
it doesn't seem right on general principles to unlock in a different
order than you nested the locks when acquiring them -- if I understand
correctly, you're suggesting lock(queue_lock), lock(tx_lock),
unlock(queue_lock), unlock(tx_lock).

Thanks,
  Roland

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