Re: [PATCH v7 0/4] lockinig/rwsem: Fix rwsem bugs & enable true lock handoff

[Waiman Long]

On 1/26/23 07:46, Ingo Molnar wrote:
> * Waiman Long <longman@xxxxxxxxxx> wrote:
>
> > v7:
> >   - Add a comment to down_read_non_owner() in patch 2.
> >   - Drop v6 patches 4 & 6 and simplify the direct rwsem lock handoff
> >     patch as suggested by PeterZ.
> >
> > v6:
> >   - Fix an error in patch 2 reported by kernel test robot.
> >
> > v5:
> >   - Drop patch 2 and replace it with 2 new patches disabling preemption on
> >     all reader functions and writer functions respectively. The other
> >     patches are adjusted accordingly.
> >
> > It turns out the current waiter optimistic spinning code does not work
> > that well if we have RT tasks in the mix. This patch series include two
> > different fixes to resolve those issues. The last 3 patches modify the
> > handoff code to implement true lock handoff similar to that of mutex.
> >
> > Waiman Long (4):
> >    locking/rwsem: Prevent non-first waiter from spinning in down_write()
> >      slowpath
> >    locking/rwsem: Disable preemption at all down_read*() and up_read()
> >      code paths
> >    locking/rwsem: Disable preemption at all down_write*() and up_write()
> >      code paths
> >    locking/rwsem: Enable direct rwsem lock handoff
> >
> >   kernel/locking/rwsem.c | 161 +++++++++++++++++++++++++++++------------
> >   1 file changed, 115 insertions(+), 46 deletions(-)
> So as a first step I've applied the first 3 patches to the locking tree,
> which are arguably fixes.

Thanks for merging into tip.

Cheers,
Longman