[dm-devel] [PATCH 1/5] blk-mq: introduce BLK_STS_DEV_RESOURCE

[Ming Lei]

On Tue, Jan 23, 2018 at 04:47:11PM +0000, Bart Van Assche wrote:
> On Wed, 2018-01-24 at 00:41 +0800, Ming Lei wrote:
> > Could you explain where to call call_rcu()?  call_rcu() can't be used in
> > IO path at all.
> 
> Can you explain what makes you think that call_rcu() can't be used in the
> I/O path? As you know call_rcu() invokes a function asynchronously. From
> Documentation/RCU/Design/Requirements/Requirements.html:
> 
>   The <tt>call_rcu()</tt> function may be used in a number of
>   situations where neither <tt>synchronize_rcu()</tt> nor
>   <tt>synchronize_rcu_expedited()</tt> would be legal,
>   including within preempt-disable code, <tt>local_bh_disable()</tt> code,
>   interrupt-disable code, and interrupt handlers.

OK, suppose it is true, do you want to change most of STS_RESOURCE in
all drivers to this way? Why can't we use the generic and simple approach
in this patch?

-- 
Ming