netdev - Re: [PATCH net] bnx2x: Fix netpoll interoperability

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Message-ID: <1429023140.7346.33.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 14 Apr 2015 07:52:20 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Yuval Mintz <Yuval.Mintz@...gic.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, bind@...s.net,
	peter@...leysoftware.com, Ariel Elior <Ariel.Elior@...gic.com>,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net] bnx2x: Fix netpoll interoperability

On Tue, 2015-04-14 at 16:35 +0300, Yuval Mintz wrote:
> Commit 9a2620c877454 ("bnx2x: prevent WARN during driver unload") switched
> the napi/busy_lock locking mechanism from spin_lock() into spin_lock_bh(),
> breaking inter-operability with netconsole, as netpoll disables interrupts
> prior to calling our napi mechanism.
> 
> This switches the driver into using atomic assignments instead of the spinlock
> mechanisms previously employed.
> 
> Signed-off-by: Yuval Mintz <Yuval.Mintz@...gic.com>
> Signed-off-by: Ariel Elior <Ariel.Elior@...gic.com>
> ---

This fix is prone to starvation of softirq handler.

Since you use 2 bits, I believe you could set one bit unconditionally to
make sure the bnx2x_low_latency_recv() will yield to softirq handler.

Please CC me and Willem on busypoll stuff, thanks !


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