From: Stanislav Fomichev <stfomichev@gmail.com>
To: Justin Iurman <justin.iurman@uliege.be>
Cc: Paolo Abeni <pabeni@redhat.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
bpf <bpf@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
Jakub Kicinski <kuba@kernel.org>
Subject: Re: new splat
Date: Tue, 1 Apr 2025 09:45:19 -0700 [thread overview]
Message-ID: <Z-wYH-gIvMd89-3d@mini-arch> (raw)
In-Reply-To: <d24ea1cc-4d32-44f9-9051-0c874f73f1c5@uliege.be>
On 04/01, Justin Iurman wrote:
> On 3/31/25 10:07, Paolo Abeni wrote:
> > Adding Justin.
> >
> > On 3/31/25 1:28 AM, Alexei Starovoitov wrote:
> > > After bpf fast forward we see this new failure:
> > >
> > > [ 138.359852] BUG: using __this_cpu_read() in preemptible [00000000]
> > > code: test_progs/9368
> > > [ 138.362686] caller is lwtunnel_xmit+0x1c/0x2e0
> > > [ 138.364363] CPU: 9 UID: 0 PID: 9368 Comm: test_progs Tainted: G
> > > O 6.14.0-10767-g8be3a12f9f26 #1092 PREEMPT
> > > [ 138.364366] Tainted: [O]=OOT_MODULE
> > > [ 138.364366] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> > > BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
> > > [ 138.364368] Call Trace:
> > > [ 138.364370] <TASK>
> > > [ 138.364375] dump_stack_lvl+0x80/0x90
> > > [ 138.364381] check_preemption_disabled+0xc6/0xe0
> > > [ 138.364385] lwtunnel_xmit+0x1c/0x2e0
> > > [ 138.364387] ip_finish_output2+0x2f9/0x850
> > > [ 138.364391] ? __ip_finish_output+0xa0/0x320
> > > [ 138.364394] ip_send_skb+0x3f/0x90
> > > [ 138.364397] udp_send_skb+0x1a6/0x3d0
> > > [ 138.364402] udp_sendmsg+0x87b/0x1000
> > > [ 138.364404] ? ip_frag_init+0x60/0x60
> > > [ 138.364406] ? reacquire_held_locks+0xcd/0x1f0
> > > [ 138.364414] ? copy_process+0x2ae0/0x2fa0
> > > [ 138.364418] ? inet_autobind+0x41/0x60
> > > [ 138.364420] ? __local_bh_enable_ip+0x79/0xe0
> > > [ 138.364422] ? inet_autobind+0x41/0x60
> > > [ 138.364424] ? inet_send_prepare+0xe7/0x1e0
> > > [ 138.364428] __sock_sendmsg+0x38/0x70
> > > [ 138.364432] ____sys_sendmsg+0x1c9/0x200
> > > [ 138.364437] ___sys_sendmsg+0x73/0xa0
> > > [ 138.364444] ? __fget_files+0xb9/0x180
> > > [ 138.364447] ? lock_release+0x131/0x280
> > > [ 138.364450] ? __fget_files+0xc3/0x180
> > > [ 138.364453] __sys_sendmsg+0x5a/0xa0
> >
> > Possibly a decoded stack trace could help.
> >
> > I think a possible suspect is:
> >
> > commit 986ffb3a57c5650fb8bf6d59a8f0f07046abfeb6
> > Author: Justin Iurman <justin.iurman@uliege.be>
> > Date: Fri Mar 14 13:00:46 2025 +0100
> >
> > net: lwtunnel: fix recursion loops
> >
> > with dev_xmit_recursion() in lwtunnel_xmit() being called in preemptible
> > scope.
>
> Correct, I came to the same conclusion based on that trace. However, I can't
> reproduce it with a PREEMPT kernel. It goes through without problem and the
> output is (as expected), i.e., "lwtunnel_xmit(): recursion limit reached on
> datapath".
For me adding the following to the config did the trick:
CONFIG_PREEMPT
CONFIG_DEBUG_PREEMPT
And reverting your patch made it go away.
next prev parent reply other threads:[~2025-04-01 16:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-30 23:28 new splat Alexei Starovoitov
2025-03-31 8:07 ` Paolo Abeni
2025-04-01 8:44 ` Justin Iurman
2025-04-01 16:45 ` Stanislav Fomichev [this message]
2025-04-01 18:16 ` Justin Iurman
2025-04-02 16:44 ` Jakub Kicinski
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