netdev - Re: [PATCH net RFC 1/2] netdevice: add might_sleep() call to napi

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Message-ID: <5253FCF6.1040808@mellanox.com>
Date:	Tue, 8 Oct 2013 15:39:18 +0300
From:	Amir Vadai <amirv@...lanox.com>
To:	Jacob Keller <jacob.e.keller@...el.com>
CC:	<netdev@...r.kernel.org>, Alex Duyck <alexander.h.duyck@...el.com>,
	Hyong-Youb Kim <hykim@...i.com>,
	Dmitry Kravkov <dmitry@...adcom.com>,
	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Subject: Re: [PATCH net RFC 1/2] netdevice: add might_sleep() call to napi_disable

On 18/09/2013 23:20, Jacob Keller wrote:
> napi_disable potentially calls msleep(1) if the NAPI_STATE_SCHED bit is
> previously set by something else. Because it does not always call msleep, it
> was difficult to track down a bug related to calling napi_disable within
> local_bh_disable()d context. This patch adds a might_sleep() call to the
> napi_disable routine in order to aid in the future debugging of similar issues.
> This will cause a BUG in drivers which have implemented busy polling in a
> similar fashion to ixgbe, and which call napi_disable inside the
> local_bh_disable()d section where the vector napi lock is taken.
> 
> Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> Cc: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
> Cc: Alex Duyck <alexander.h.duyck@...el.com>
> Cc: Hyong-Youb Kim <hykim@...i.com>
> Cc: Amir Vadai <amirv@...lanox.com>
> Cc: Dmitry Kravkov <dmitry@...adcom.com>
> ---
>  include/linux/netdevice.h |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 3de49ac..81dab00 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -483,6 +483,8 @@ extern void napi_hash_del(struct napi_struct *napi);
>   */
>  static inline void napi_disable(struct napi_struct *n)
>  {
> +	might_sleep();
> +
>  	set_bit(NAPI_STATE_DISABLE, &n->state);
>  	while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
>  		msleep(1);
> 

Works ok with mlx4_en driver.

Acked-By: Amir Vadai <amirv@...lanox.com>
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