From: Roland Dreier <rdreier@cisco•com>
To: "aluno3\@poczta.onet.pl" <aluno3@poczta•onet.pl>
Cc: general@lists•openfabrics.org, netdev@vger•kernel.org
Subject: Re: [ofa-general] NetEffect, iw_nes and kernel warning
Date: Tue, 27 Jan 2009 15:53:16 -0800 [thread overview]
Message-ID: <adawscgwbkj.fsf@cisco.com> (raw)
In-Reply-To: <497EF9AC.70104@poczta.onet.pl> (aluno3@poczta.onet.pl's message of "Tue, 27 Jan 2009 13:10:20 +0100")
Interesting... looks like an unfortunate interaction with unclear
locking rules. See below for full explanation.
BTW, what workload are you running to hit this?
I assume you have CONFIG_HIGHMEM set?
> WARNING: at kernel/softirq.c:136 local_bh_enable+0x9b/0xa0()
I assume this is
WARN_ON_ONCE(in_irq() || irqs_disabled());
The interesting parts of the stack trace seem to be (reversing the order
so the story makes sense):
[<e8e3f815>] nes_netdev_start_xmit+0x815/0x8a0 [iw_nes]
nes_netdev_start_xmit() calls skb_linearize() for nonlinear skbs it
can't handle, which calls __pskb_pull_tail():
[<c048982c>] __pskb_pull_tail+0x5c/0x2e0
__pskb_pull_tail() calls skb_copy_bits():
[<c0489c05>] skb_copy_bits+0x155/0x290
At least in some cases, skb_copy_bits() calls kmap_skb_frag() and more
to the point kunmap_skb_frag(), which looks like:
static inline void kunmap_skb_frag(void *vaddr)
{
kunmap_atomic(vaddr, KM_SKB_DATA_SOFTIRQ);
#ifdef CONFIG_HIGHMEM
local_bh_enable();
#endif
}
which leads to:
[<c012a79b>] local_bh_enable+0x9b/0xa0
which hits the irqs_disabled() warning because iw_nes is using LLTX, and
nes_netdev_start_xmit() does:
local_irq_save(flags);
if (!spin_trylock(&nesnic->sq_lock)) {
at the very beginning.
The best solution is probably for iw_nes to stop using LLTX and use the
main netdev lock... but actually I still don't see how it's safe for a
net driver to call skb_linearize() from its transmit routine, since
there's a chance that that will unconditionally enable BHs?
- R.
next parent reply other threads:[~2009-01-27 23:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <497EF9AC.70104@poczta.onet.pl>
2009-01-27 23:53 ` Roland Dreier [this message]
2009-01-28 0:07 ` [ofa-general] NetEffect, iw_nes and kernel warning David Miller
2009-01-28 0:17 ` Stephen Hemminger
2009-01-28 16:36 ` Tung, Chien Tin
2009-01-28 18:05 ` Roland Dreier
2009-01-28 19:05 ` Stephen Hemminger
2009-01-28 21:52 ` Roland Dreier
2009-01-30 6:57 ` Herbert Xu
2009-01-30 8:22 ` Eilon Greenstein
2009-01-30 16:25 ` Stephen Hemminger
2009-01-30 17:35 ` Roland Dreier
2009-01-30 21:51 ` David Miller
2009-01-31 3:54 ` Roland Dreier
2009-04-21 9:09 ` Lennert Buytenhek
2009-04-21 12:49 ` Herbert Xu
2009-04-21 12:50 ` Herbert Xu
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