Re: [PATCH v9 3/9] PCI: Create PCI library functions in support of DOE mailboxes.

[Ira Weiny]

On Wed, Jun 01, 2022 at 06:59:09AM -0700, Davidlohr Bueso wrote:
> On Tue, 31 May 2022, Ira Weiny wrote:
> > Thinking about it I don't see a benefit to a rwlock.  We don't have multiple
> > readers.
> 
> ... but you have concurrent workqueues reading the value of cur_task.

No, concurrent workqueues are reading the value of different DOE mailboxes'
cur_task.  Each mailbox has it's own lock for its current task.

This is a multiple writers to a single reader pattern.  The lock serializes
driver requests (possibly from different threads) into the single mailbox as
well as signaling when the cur_task is done; retire_cur_task().

At the same time multiple mailboxes can be running parallel.

I don't think taking the lock in doe_statemachine_work() is technically
necessary.   But I left it there for completeness because if the queue depth is
increased like it was in Jonathans original code the locking around cur_task
will need to be adjusted in this area.

Ira

> 
> Thanks,
> Davidlohr