Re: [PATCH 2/5] rds: ib: replace spin_lock_irq with spin_lock_irqsave

["santosh.shilimkar@oracle.com" <santosh.shilimkar@oracle.com>]

On 3/11/17 6:33 PM, Yanjun Zhu wrote:
> Sorry. I have no test case to show some issue.
> But from Linux Kernel Development Second Edition by Robert Love.
>
Yes I know the book and what the API does :D

> Use spin_lock_irq is dangerous since spin_unlock_irq unconditionally
> enables interrupts.
>
> We can assume the following scenario:
>
> --->the interrupt is disabled.
>
>         spin_lock_irq(lock_ptr);   <---this will disable interrupt again
>         list_del(&ic->ib_node);
>         spin_unlock_irq(lock_ptr); <---this will enable interrupt
>
> ---->the interrupt is enabled.
>
> our code change the state of interrupt. This will make potential risk.
> But spin_lock_irqsave/spin_unlock_irqrestore will not make potential risk.
>
ic is well protected for any possible race and hence I asked
if you had any test case. Please re-post the series again with
the subject patch dropper for Dave to pick it up.

Regards,
Santosh