From: Ray Jui <ray.jui@broadcom.com>
To: Wolfram Sang <wsa@kernel.org>
Cc: Dhananjay Phadke <dphadke@linux.microsoft.com>,
Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
Ray Jui <rjui@broadcom.com>,
bcm-kernel-feedback-list@broadcom.com
Subject: Re: [PATCH] i2c: iproc: fix race between client unreg and isr
Date: Mon, 27 Jul 2020 08:42:33 -0700 [thread overview]
Message-ID: <4cf12c92-889d-ffbf-f8de-c1e08cfb8ce9@broadcom.com> (raw)
In-Reply-To: <20200725101815.GA1519@ninjato>
Hi Wolfram,
On 7/25/2020 3:18 AM, Wolfram Sang wrote:
>
>> 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.
>
Can you confirm that even if we have irq pending at the i2c IP core
level, as long as we execute Step 2. below (to disable/mask all slave
interrupts), after 'enable_irq' is called, we still will not receive any
further i2c slave interrupt?
Basically I'm asking if interrupts will be "cached" at the GIC
controller level after 'disable_irq' is called. As long as that is not
the case, then I think we are good.
The goal of course is to ensure there's no further slave interrupts
after 'enable_irq' in Step 3 below.
Thanks!
> 2. disable all slave interrupts
>
> 3. enable_irq()
>
> 4. clean up the rest (pointer, address)
>
> Or am I overlooking something?
>
next prev parent reply other threads:[~2020-07-27 15:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-18 23:39 [PATCH] i2c: iproc: fix race between client unreg and isr Dhananjay Phadke
2020-07-19 7:59 ` Rayagonda Kokatanur
2020-07-20 17:40 ` Scott Branden
2020-07-20 17:49 ` Ray Jui
2020-07-22 10:41 ` Wolfram Sang
2020-07-22 15:51 ` Ray Jui
2020-07-22 16:55 ` Ray Jui
2020-07-23 0:58 ` Dhananjay Phadke
2020-07-25 10:18 ` Wolfram Sang
2020-07-27 4:32 ` Rayagonda Kokatanur
2020-07-27 15:42 ` Ray Jui [this message]
2020-07-27 17:38 ` Dhananjay Phadke
2020-07-27 18:13 ` Wolfram Sang
2020-07-27 20:26 ` Wolfram Sang
2020-07-27 20:43 ` Ray Jui
2020-08-05 9:17 ` Wolfram Sang
2020-08-07 16:40 ` Ray Jui
2020-08-07 17:38 ` Dhananjay Phadke
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