![]() Fix lockdep warning with GRE, iptables and Speedtouch ADSL, PPP over ATM. On Sat, Sep 02, 2006 at 08:39:28PM +0000, Krzysztof Halasa wrote: > > ======================================================= > [ INFO: possible circular locking dependency detected ] > ------------------------------------------------------- > swapper/0 is trying to acquire lock: > (&dev->queue_lock){-+..}, at: [<c02c8c46>] dev_queue_xmit+0x56/0x290 > > but task is already holding lock: > (&dev->_xmit_lock){-+..}, at: [<c02c8e14>] dev_queue_xmit+0x224/0x290 > > which lock already depends on the new lock. This turns out to be a genuine bug. The queue lock and xmit lock are intentionally taken out of order. Two things are supposed to prevent dead-locks from occuring: 1) When we hold the queue_lock we're supposed to only do try_lock on the tx_lock. 2) We always drop the queue_lock after taking the tx_lock and before doing anything else. > > the existing dependency chain (in reverse order) is: > > -> #1 (&dev->_xmit_lock){-+..}: > [<c012e7b6>] lock_acquire+0x76/0xa0 > [<c0336241>] _spin_lock_bh+0x31/0x40 > [<c02d25a9>] dev_activate+0x69/0x120 This path obviously breaks assumption 1) and therefore can lead to ABBA dead-locks. I've looked at the history and there seems to be no reason for the lock to be held at all in dev_watchdog_up. The lock appeared in day one and even there it was unnecessary. In fact, people added __dev_watchdog_up precisely in order to get around the tx lock there. The function dev_watchdog_up is already serialised by rtnl_lock since its only caller dev_activate is always called under it. So here is a simple patch to remove the tx lock from dev_watchdog_up. In 2.6.19 we can eliminate the unnecessary __dev_watchdog_up and replace it with dev_watchdog_up. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net> |
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act_api.c | ||
act_gact.c | ||
act_ipt.c | ||
act_mirred.c | ||
act_pedit.c | ||
act_police.c | ||
act_simple.c | ||
cls_api.c | ||
cls_basic.c | ||
cls_fw.c | ||
cls_route.c | ||
cls_rsvp.c | ||
cls_rsvp.h | ||
cls_rsvp6.c | ||
cls_tcindex.c | ||
cls_u32.c | ||
em_cmp.c | ||
em_meta.c | ||
em_nbyte.c | ||
em_text.c | ||
em_u32.c | ||
ematch.c | ||
estimator.c | ||
Kconfig | ||
Makefile | ||
sch_api.c | ||
sch_atm.c | ||
sch_blackhole.c | ||
sch_cbq.c | ||
sch_dsmark.c | ||
sch_fifo.c | ||
sch_generic.c | ||
sch_gred.c | ||
sch_hfsc.c | ||
sch_htb.c | ||
sch_ingress.c | ||
sch_netem.c | ||
sch_prio.c | ||
sch_red.c | ||
sch_sfq.c | ||
sch_tbf.c | ||
sch_teql.c |