netdev - Re: [PATCH resend 1/3] Revert "net: fec: fix missing napi

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Message-ID: <20130427191600.GA30373@electric-eye.fr.zoreil.com>
Date:	Sat, 27 Apr 2013 21:16:00 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Frank Li <lznuaa@...il.com>
Cc:	Robert Schwebel <r.schwebel@...gutronix.de>,
	David Miller <davem@...emloft.net>,
	Lucas Stach <l.stach@...gutronix.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Frank.Li@...escale.com" <Frank.Li@...escale.com>,
	Fabio Estevam <festevam@...il.com>,
	Shawn Guo <shawn.guo@...aro.org>
Subject: Re: [PATCH resend 1/3] Revert "net: fec: fix missing napi_disable
 call"

Frank Li <lznuaa@...il.com> :
> 2013/4/27, Francois Romieu <romieu@...zoreil.com>:
[...]
> > napi_disable may sleep.
> >
> > fec_restart can be called with spinlock held in fec_enet_adjust_link
> 
> You are right. Spin lock in FEC enet adjust link can be removed when
> remove spinlock in tx and RX.

fec_restart is also called from the netdev watchdog handler (fec_timeout)
and tasklet can't sleep either. You should imho schedule_work from
fec_timeout.

How is the driver supposed to avoid the napi context
fec_enet_tx:netif_queue_stopped vs fec_enet_start_xmit:netif_stop_queue
race since both can run on different cpu without any read/write ordering
enforcement between one thread netif_* and its peer {dirty/cur}_tx ?

-- 
Ueimor
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