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Subject: Re: [PATCH] net/xfrm/xfrm_ipcomp: Use {get,put}_cpu_light
To:     Juri Lelli <juri.lelli@redhat.com>, rostedt@goodmis.org,
        tglx@linutronix.de, bigeasy@linutronix.de
Cc:     linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        williams@redhat.com
References: <20190717072019.13681-1-juri.lelli@redhat.com>
From:   Daniel Bristot de Oliveira <daniel@bristot.me>
Message-ID: <ed2ab5b2-2499-2f0b-9cd9-a84f1d528c4d@bristot.me>
Date:   Wed, 17 Jul 2019 09:22:43 +0200
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On 17/07/2019 09:20, Juri Lelli wrote:
> The following BUG has been reported while running ipsec tests.
> 
>  BUG: scheduling while atomic: irq/78-eno3-rx-/12023/0x00000002
>  Modules linked in: ipcomp xfrm_ipcomp ...
>  Preemption disabled at:
>  [<ffffffffc0b29730>] ipcomp_input+0xd0/0x9a0 [xfrm_ipcomp]
>  CPU: 1 PID: 12023 Comm: irq/78-eno3-rx- Kdump: loaded Not tainted [...] #1
>  Hardware name: [...]
>  Call Trace:
>   dump_stack+0x5c/0x80
>   ? ipcomp_input+0xd0/0x9a0 [xfrm_ipcomp]
>   __schedule_bug.cold.81+0x44/0x51
>   __schedule+0x5bf/0x6a0
>   schedule+0x39/0xd0
>   rt_spin_lock_slowlock_locked+0x10e/0x2b0
>   rt_spin_lock_slowlock+0x50/0x80
>   get_page_from_freelist+0x609/0x1560
>   ? zlib_updatewindow+0x5a/0xd0
>   __alloc_pages_nodemask+0xd9/0x280
>   ipcomp_input+0x299/0x9a0 [xfrm_ipcomp]
>   xfrm_input+0x5e3/0x960
>   xfrm4_ipcomp_rcv+0x34/0x50
>   ip_local_deliver_finish+0x22d/0x250
>   ip_local_deliver+0x6d/0x110
>   ? ip_rcv_finish+0xac/0x480
>   ip_rcv+0x28e/0x3f9
>   ? packet_rcv+0x43/0x4c0
>   __netif_receive_skb_core+0xb7c/0xd10
>   ? inet_gro_receive+0x8e/0x2f0
>   netif_receive_skb_internal+0x4a/0x160
>   napi_gro_receive+0xee/0x110
>   tg3_rx+0x2a8/0x810 [tg3]
>   tg3_poll_work+0x3b3/0x830 [tg3]
>   tg3_poll_msix+0x3b/0x170 [tg3]
>   net_rx_action+0x1ff/0x470
>   ? __switch_to_asm+0x41/0x70
>   do_current_softirqs+0x223/0x3e0
>   ? irq_thread_check_affinity+0x20/0x20
>   __local_bh_enable+0x51/0x60
>   irq_forced_thread_fn+0x5e/0x80
>   ? irq_finalize_oneshot.part.45+0xf0/0xf0
>   irq_thread+0x13d/0x1a0
>   ? wake_threads_waitq+0x30/0x30
>   kthread+0x112/0x130
>   ? kthread_create_worker_on_cpu+0x70/0x70
>   ret_from_fork+0x35/0x40
> 
> The problem resides in the fact that get_cpu() called from ipcomp_input()
> disables preemption, and that triggers the scheduling while atomic BUG further
> down the callpath chain of get_page_from_freelist(), i.e.,
> 
>   ipcomp_input
>     ipcomp_decompress
>       <-- get_cpu()
>       alloc_page(GFP_ATOMIC)
>         alloc_pages(GFP_ATOMIC, 0)
>           alloc_pages_current
>             __alloc_pages_nodemask
>               get_page_from_freelist
>                 (try_this_zone:) rmqueue
>                   rmqueue_pcplist
>                     __rmqueue_pcplist
>                       rmqueue_bulk
>                         <-- spin_lock(&zone->lock) - BUG
> 
> Fix this by using {get,put}_cpu_light() in ipcomp_decompress().
> 
> Signed-off-by: Juri Lelli <juri.lelli@redhat.com>

Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>

Thanks!
-- Daniel