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

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Message-ID: <20200725101815.GA1519@ninjato>
Date:   Sat, 25 Jul 2020 12:18:16 +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


> I think the following sequence needs to be implemented to make this
> safe, i.e., after 'synchronize_irq', no further slave interrupt will be
> fired.
> 
> In 'bcm_iproc_i2c_unreg_slave':
> 
> 1. Set an atomic variable 'unreg_slave' (I'm bad in names so please come
> up with a better name than this)
> 
> 2. Disable all slave interrupts
> 
> 3. synchronize_irq
> 
> 4. Set slave to NULL
> 
> 5. Erase slave addresses

What about this in unreg_slave?

1. disable_irq()
	This includes synchronize_irq() and avoids the race. Because irq
	will be masked at interrupt controller level, interrupts coming
	in at the I2C IP core level should still be pending once we
	reenable the irq.

2. disable all slave interrupts

3. enable_irq()

4. clean up the rest (pointer, address)

Or am I overlooking something?


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