From: Roland Dreier <roland@topspin.com>
To: hadi@cyberus.ca
Cc: netdev@oss.sgi.com, "David S. Miller" <davem@davemloft.net>,
openib-general@openib.org
Subject: Re: LLTX and netif_stop_queue
Date: Sun, 19 Dec 2004 15:16:58 -0800 [thread overview]
Message-ID: <527jndnaj9.fsf@topspin.com> (raw)
In-Reply-To: <1103497592.1046.235.camel@jzny.localdomain> (jamal's message of "19 Dec 2004 18:06:32 -0500")
Roland> This seems a little risky. I can't point to a specific
Roland> deadlock but it doesn't seem right on general principles
Roland> to unlock in a different order than you nested the locks
Roland> when acquiring them -- if I understand correctly, you're
Roland> suggesting lock(queue_lock), lock(tx_lock),
Roland> unlock(queue_lock), unlock(tx_lock).
jamal> There is no deadlock. Thats exactly how things work. Try
jamal> the patches i posted.
Thinking about it more, I guess it's OK. I was just think about the
basic general rule that locks need to be acquired/released in LIFO
order to avoid deadlock (eg lock(A), lock(B), unlock(B), unlock(A)).
However in this case unlocking queue_lock after acquiring the driver's
tx_lock seems to be OK because the driver does a trylock on tx_lock in
the xmit path, so it can't deadlock. At worst the trylock will just
fail to get the lock.
Thanks,
Roland
next prev parent reply other threads:[~2004-12-19 23:16 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-17 21:57 LLTX and netif_stop_queue Roland Dreier
2004-12-18 5:44 ` David S. Miller
2004-12-18 15:35 ` Roland Dreier
2004-12-18 17:58 ` Roland Dreier
2004-12-18 18:26 ` Roland Dreier
2004-12-19 19:33 ` jamal
2004-12-19 19:31 ` jamal
2004-12-19 19:54 ` jamal
2004-12-19 20:02 ` Jamal Hadi Salim
2004-12-19 22:35 ` Roland Dreier
2004-12-19 23:06 ` jamal
2004-12-19 23:16 ` Roland Dreier [this message]
2004-12-22 18:49 ` Eric Lemoine
2004-12-23 4:29 ` David S. Miller
2004-12-23 4:38 ` Roland Dreier
2004-12-23 9:10 ` Eric Lemoine
2004-12-23 16:37 ` Patrick McHardy
2004-12-23 18:11 ` Eric Lemoine
2004-12-24 16:10 ` Eric Lemoine
2004-12-28 13:31 ` jamal
2005-01-02 23:30 ` Eric Lemoine
2005-01-03 7:41 ` Eric Lemoine
2005-01-03 15:04 ` jamal
2005-01-03 15:48 ` Eric Lemoine
2005-01-03 15:57 ` Roland Dreier
2005-01-03 16:41 ` Eric Lemoine
2005-01-03 16:54 ` Roland Dreier
2005-01-03 17:07 ` Eric Lemoine
2005-01-03 17:12 ` Grant Grundler
2005-01-04 4:18 ` jamal
2005-01-19 22:47 ` David S. Miller
2005-01-19 23:18 ` Stephen Hemminger
2005-01-19 23:41 ` David S. Miller
2005-01-20 0:02 ` [openib-general] " Jeff Garzik
2005-01-20 0:46 ` Stephen Hemminger
2005-01-20 0:47 ` David S. Miller
2005-01-20 0:47 ` Francois Romieu
2005-01-20 0:52 ` David S. Miller
2005-01-20 1:17 ` Francois Romieu
2005-01-20 0:46 ` [PATCH]: was " David S. Miller
2005-01-20 3:14 ` Andi Kleen
2005-01-20 7:05 ` David S. Miller
2005-01-20 3:43 ` Roland Dreier
2005-01-20 7:05 ` David S. Miller
2005-01-20 13:51 ` Tommy Christensen
2005-01-20 21:34 ` David S. Miller
2005-01-20 21:56 ` Grant Grundler
2005-01-21 1:01 ` David S. Miller
2005-01-22 3:17 ` Roland Dreier
2005-01-22 3:53 ` David S. Miller
2005-01-20 21:41 ` David S. Miller
2005-01-20 16:56 ` Stephen Hemminger
2005-01-21 10:54 ` Lennert Buytenhek
2005-01-26 6:27 ` David S. Miller
2005-01-26 13:25 ` Lennert Buytenhek
2005-01-27 6:32 ` David S. Miller
2005-01-27 7:16 ` Andi Kleen
2005-01-27 7:22 ` David S. Miller
2005-01-27 8:26 ` Andi Kleen
2005-01-20 19:16 ` Jeff Garzik
2005-01-20 4:01 ` jamal
2005-01-20 5:18 ` David S. Miller
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