linux-kernel - Re: [PATCH] i2c: iproc: fix race between client unreg and isr

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Message-ID: <20200722104128.GK1030@ninjato>
Date:   Wed, 22 Jul 2020 12:41:28 +0200
From:   Wolfram Sang <wsa@...nel.org>
To:     Ray Jui <ray.jui@...adcom.com>
Cc:     Dhananjay Phadke <dphadke@...ux.microsoft.com>,
        Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ray Jui <rjui@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH] i2c: iproc: fix race between client unreg and isr


> > +	synchronize_irq(iproc_i2c->irq);
> 
> If one takes a look at the I2C slave ISR routine, there are places where
> IRQ can be re-enabled in the ISR itself. What happens after we mask all
> slave interrupt and when 'synchronize_irq' is called, which I suppose is
> meant to wait for inflight interrupt to finish where there's a chance
> the interrupt can be re-enable again? How is one supposed to deal with that?

I encountered the same problem with the i2c-rcar driver before I left
for my holidays.

> > +	iproc_i2c->slave = NULL;
> > +
> >  	/* Erase the slave address programmed */
> >  	tmp = iproc_i2c_rd_reg(iproc_i2c, S_CFG_SMBUS_ADDR_OFFSET);
> >  	tmp &= ~BIT(S_CFG_EN_NIC_SMB_ADDR3_SHIFT);
> > 

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