netdev - Re: [PATCH net RFC 2/2] ixgbe: fix sleep bug caused by napi_disable inside local_bh

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Message-ID: <20130919213254.GC31672@electric-eye.fr.zoreil.com>
Date:	Thu, 19 Sep 2013 23:32:54 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	"Keller, Jacob E" <jacob.e.keller@...el.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Duyck, Alexander H" <alexander.h.duyck@...el.com>,
	Hyong-Youb Kim <hykim@...i.com>,
	Dmitry Kravkov <dmitry@...adcom.com>,
	Amir Vadai <amirv@...lanox.com>,
	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Subject: Re: [PATCH net RFC 2/2] ixgbe: fix sleep bug caused by napi_disable
 inside local_bh_disable()d context

Keller, Jacob E <jacob.e.keller@...el.com> :
[...]
> I know that we need local_bh_disable around the qv_lock_napi code because
> it uses spin_lock instead of spin_lock_bh. I believe the reason we need bh
> disabled around the entire context is so that the small window between
> failed calls to qv_lock_napi don't get interrupted and continue to have
> busy_poll lock the q_vector over and over.

Thanks for explaining the intent. I'll do my homework.

> I have to move the local_bh_disable in order to put napi_disable outside
> of the call since napi_disable could sleep, causing a scheduling while
> atomic BUG.

I am in violent agreement with this part.

--
Ueimor
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