linux-kernel - Re: [PATCH net] net: systemport: Fix wake-up interrupt race during resume

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Date:   Tue, 02 Oct 2018 17:35:26 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     f.fainelli@...il.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: systemport: Fix wake-up interrupt race during
 resume

From: Florian Fainelli <f.fainelli@...il.com>
Date: Tue,  2 Oct 2018 16:52:03 -0700

> The AON_PM_L2 is normally used to trigger and identify the source of a
> wake-up event. Since the RX_SYS clock is no longer turned off, we also
> have an interrupt being sent to the SYSTEMPORT INTRL_2_0 controller, and
> that interrupt remains active up until the magic packet detector is
> disabled which happens much later during the driver resumption.
> 
> The race happens if we have a CPU that is entering the SYSTEMPORT
> INTRL2_0 handler during resume, and another CPU has managed to clear the
> wake-up interrupt during bcm_sysport_resume_from_wol(). In that case, we
> have the first CPU stuck in the interrupt handler with an interrupt
> cause that has been cleared under its feet, and so we keep returning
> IRQ_NONE and we never make any progress.
> 
> This was not a problem before because we would always turn off the
> RX_SYS clock during WoL, so the SYSTEMPORT INTRL2_0 would also be turned
> off as well, thus not latching the interrupt.
> 
> The fix is to make sure we do not enable either the MPD or
> BRCM_TAG_MATCH interrupts since those are redundant with what the
> AON_PM_L2 interrupt controller already processes and they would cause
> such a race to occur.
> 
> Fixes: bb9051a2b230 ("net: systemport: Add support for WAKE_FILTER")
> Fixes: 83e82f4c706b ("net: systemport: add Wake-on-LAN support")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

Applied, thanks Florian.