netdev - Re: [PATCH v2] drop_monitor: dont sleep in atomic context

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Date:	Mon, 4 Jun 2012 06:49:37 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] drop_monitor: dont sleep in atomic context

On Mon, Jun 04, 2012 at 12:18:19PM +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> drop_monitor calls several sleeping functions while in atomic context.
> 
>  BUG: sleeping function called from invalid context at mm/slub.c:943
>  in_atomic(): 1, irqs_disabled(): 0, pid: 2103, name: kworker/0:2
>  Pid: 2103, comm: kworker/0:2 Not tainted 3.5.0-rc1+ #55
>  Call Trace:
>   [<ffffffff810697ca>] __might_sleep+0xca/0xf0
>   [<ffffffff811345a3>] kmem_cache_alloc_node+0x1b3/0x1c0
>   [<ffffffff8105578c>] ? queue_delayed_work_on+0x11c/0x130
>   [<ffffffff815343fb>] __alloc_skb+0x4b/0x230
>   [<ffffffffa00b0360>] ? reset_per_cpu_data+0x160/0x160 [drop_monitor]
>   [<ffffffffa00b022f>] reset_per_cpu_data+0x2f/0x160 [drop_monitor]
>   [<ffffffffa00b03ab>] send_dm_alert+0x4b/0xb0 [drop_monitor]
>   [<ffffffff810568e0>] process_one_work+0x130/0x4c0
>   [<ffffffff81058249>] worker_thread+0x159/0x360
>   [<ffffffff810580f0>] ? manage_workers.isra.27+0x240/0x240
>   [<ffffffff8105d403>] kthread+0x93/0xa0
>   [<ffffffff816be6d4>] kernel_thread_helper+0x4/0x10
>   [<ffffffff8105d370>] ? kthread_freezable_should_stop+0x80/0x80
>   [<ffffffff816be6d0>] ? gs_change+0xb/0xb
> 
> Rework the logic to call the sleeping functions in right context.
> 
> Use standard timer/workqueue api to let system chose any cpu to perform
> the allocation and netlink send.
> 
> Also avoid a loop if reset_per_cpu_data() cannot allocate memory :
> use mod_timer() to wait 1/10 second before next try.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Neil Horman <nhorman@...driver.com>
Reviewed-by: Neil Horman <nhorman@...driver.com>

Thanks Eric!
Neil

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