netdev - Re: [PATCH net] net: dsa: bcm_sf2: Fix race condition while unmasking interrupts

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Message-Id: <20160825.165016.515976592954248193.davem@redhat.com>
Date:   Thu, 25 Aug 2016 16:50:16 -0700 (PDT)
From:   David Miller <davem@...hat.com>
To:     f.fainelli@...il.com
Cc:     netdev@...r.kernel.org, andrew@...n.ch,
        vivien.didelot@...oirfairelinux.com
Subject: Re: [PATCH net] net: dsa: bcm_sf2: Fix race condition while
 unmasking interrupts

From: Florian Fainelli <f.fainelli@...il.com>
Date: Wed, 24 Aug 2016 11:01:20 -0700

> We kept shadow copies of which interrupt sources we have enabled and
> disabled, but due to an order bug in how intrl2_mask_clear was defined,
> we could run into the following scenario:
> 
> CPU0					CPU1
> intrl2_1_mask_clear(..)
> sets INTRL2_CPU_MASK_CLEAR
> 					bcm_sf2_switch_1_isr
> 					read INTRL2_CPU_STATUS and masks with stale
> 					irq1_mask value
> updates irq1_mask value
> 
> Which would make us loop again and again trying to process and interrupt
> we are not clearing since our copy of whether it was enabled before
> still indicates it was not. Fix this by updating the shadow copy first,
> and then unasking at the HW level.
> 
> Fixes: 246d7f773c13 ("net: dsa: add Broadcom SF2 switch driver")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

Applied and queued up for -stable, thanks.