Re: [PATCH v3 16/20] iocost: Use sequence counter with associated spinlock

Daniel Wagner
2020-06-30T07:12:04Z

On Tue, Jun 30, 2020 at 07:44:48AM +0200, Ahmed S. Darwish wrote:
> A sequence counter write side critical section must be protected by some
> form of locking to serialize writers. A plain seqcount_t does not
> contain the information of which lock must be held when entering a write
> side critical section.
>
> Use the new seqcount_spinlock_t data type, which allows to associate a
> spinlock with the sequence counter. This enables lockdep to verify that
> the spinlock used for writer serialization is held when the write side
> critical section is entered.
>
> If lockdep is disabled this lock association is compiled out and has
> neither storage size nor runtime overhead.
>
> Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>

Reviewed-by: Daniel Wagner <dwagner@suse.de>