Re: [PATCH v2 06/28] locking/rwlocks: Add contention detection for rwlocks

[Waiman Long]

On 2/9/21 10:32 PM, Waiman Long wrote:
> On 2/2/21 1:57 PM, Ben Gardon wrote:
> > rwlocks do not currently have any facility to detect contention
> > like spinlocks do. In order to allow users of rwlocks to better manage
> > latency, add contention detection for queued rwlocks.
> >
> > CC: Ingo Molnar <mingo@xxxxxxxxxx>
> > CC: Will Deacon <will@xxxxxxxxxx>
> > Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Acked-by: Davidlohr Bueso <dbueso@xxxxxxx>
> > Acked-by: Waiman Long <longman@xxxxxxxxxx>
> > Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
> > ---
> >   include/asm-generic/qrwlock.h | 24 ++++++++++++++++++------
> >   include/linux/rwlock.h        |  7 +++++++
> >   2 files changed, 25 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/asm-generic/qrwlock.h 
> > b/include/asm-generic/qrwlock.h
> > index 84ce841ce735..0020d3b820a7 100644
> > --- a/include/asm-generic/qrwlock.h
> > +++ b/include/asm-generic/qrwlock.h
> > @@ -14,6 +14,7 @@
> >   #include <asm/processor.h>
> >     #include <asm-generic/qrwlock_types.h>
> > +#include <asm-generic/qspinlock.h>
>
> As said in another thread, qspinlock and qrwlock can be independently 
> enabled for an architecture. So we shouldn't include qspinlock.h here. 
> Instead, just include the regular linux/spinlock.h file to make sure 
> that arch_spin_is_locked() is available.

The csky architecture uses qrwlock but not qspinlock. So this patch can 
be problematic when compiling for csky.

Cheers,
Longman