linux-kernel - Re: [Openipmi-developer] [PATCH 0/1] Fix race in ipmi timer cleanup

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Message-ID: <d93bbba3-16e0-7c68-2fec-fde840bd7072@gmail.com>
Date:   Mon, 16 Sep 2019 10:01:37 -0400
From:   Jes Sorensen <jes.sorensen@...il.com>
To:     minyard@....org
Cc:     openipmi-developer@...ts.sourceforge.net, kernel-team@...com,
        linux-kernel@...r.kernel.org
Subject: Re: [Openipmi-developer] [PATCH 0/1] Fix race in ipmi timer cleanup

On 9/14/19 9:08 PM, Corey Minyard wrote:
>>
>>>
>>> {disable,enable}_si_irq() themselves are racy:
>>>
>>> static inline bool disable_si_irq(struct smi_info *smi_info)
>>> {
>>>         if ((smi_info->io.irq) && (!smi_info->interrupt_disabled)) {
>>>                 smi_info->interrupt_disabled = true;
>>>
>>> Basically interrupt_disabled need to be atomic here to have any value,
>>> unless you ensure to have a spin lock around every access to it.
>>
>> It needs to be atomic, yes, but I think just adding the spinlock like
>> I suggested will work.  You are right, the check for timer_running is
>> not necessary here, and I'm fine with removing it, but there are other
>> issues with interrupt_disabled (as you said) and with memory ordering
>> in the timer case.  So even if you remove the timer running check, the
>> lock is still required here.
> 
> It turns out you were right, all that really needs to be done is the
> del_timer_sync().  I've added your patch to my queue.
> 
> Sorry for the trouble.

Awesome!

Sorry I was going to get back and look at it again, but Linux Plumbers
and playing sardine i a tin can got in the way.

Cheers,
Jes