Re: [PATCH v5 1/6] qspinlock: powerpc support qspinlock

[Benjamin Herrenschmidt <benh@au1.ibm.com>]

On Fri, 2016-06-03 at 11:32 +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2016-06-02 at 17:22 +0800, Pan Xinhui wrote:
> > 
> > Base code to enable qspinlock on powerpc. this patch add some
> > #ifdef
> > here and there. Although there is no paravirt related code, we can
> > successfully build a qspinlock kernel after apply this patch.
> This is missing the IO_SYNC stuff ... It means we'll fail to do a
> full
> sync to order vs MMIOs.
> 
> You need to add that back in the unlock path.

Well, and in the lock path as well...

Cheers,
Ben.

> > 
> > Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
> > ---
> >  arch/powerpc/include/asm/qspinlock.h      | 26
> > ++++++++++++++++++++++++++
> >  arch/powerpc/include/asm/spinlock.h       | 27 +++++++++++++++----
> > --------
> >  arch/powerpc/include/asm/spinlock_types.h |  4 ++++
> >  arch/powerpc/lib/locks.c                  |  4 ++++
> >  4 files changed, 49 insertions(+), 12 deletions(-)
> >  create mode 100644 arch/powerpc/include/asm/qspinlock.h
> > 
> > diff --git a/arch/powerpc/include/asm/qspinlock.h
> > b/arch/powerpc/include/asm/qspinlock.h
> > new file mode 100644
> > index 0000000..fc83cd2
> > --- /dev/null
> > +++ b/arch/powerpc/include/asm/qspinlock.h
> > @@ -0,0 +1,26 @@
> > +#ifndef _ASM_POWERPC_QSPINLOCK_H
> > +#define _ASM_POWERPC_QSPINLOCK_H
> > +
> > +#include <asm-generic/qspinlock_types.h>
> > +
> > +#define SPIN_THRESHOLD (1 << 15)
> > +#define queued_spin_unlock queued_spin_unlock
> > +
> > +static inline void native_queued_spin_unlock(struct qspinlock
> > *lock)
> > +{
> > +	u8 *locked = (u8 *)lock;
> > +#ifdef __BIG_ENDIAN
> > +	locked += 3;
> > +#endif
> > +	/* no load/store can be across the unlock()*/
> > +	smp_store_release(locked, 0);
> > +}
> > +
> > +static inline void queued_spin_unlock(struct qspinlock *lock)
> > +{
> > +	native_queued_spin_unlock(lock);
> > +}
> > +
> > +#include <asm-generic/qspinlock.h>
> > +
> > +#endif /* _ASM_POWERPC_QSPINLOCK_H */
> > diff --git a/arch/powerpc/include/asm/spinlock.h
> > b/arch/powerpc/include/asm/spinlock.h
> > index 523673d..4359ee6 100644
> > --- a/arch/powerpc/include/asm/spinlock.h
> > +++ b/arch/powerpc/include/asm/spinlock.h
> > @@ -52,6 +52,20 @@
> >  #define SYNC_IO
> >  #endif
> >  
> > +#if defined(CONFIG_PPC_SPLPAR)
> > +/* We only yield to the hypervisor if we are in shared processor
> > mode */
> > +#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca-
> > > 
> > > lppaca_ptr))
> > +extern void __spin_yield(arch_spinlock_t *lock);
> > +extern void __rw_yield(arch_rwlock_t *lock);
> > +#else /* SPLPAR */
> > +#define __spin_yield(x)	barrier()
> > +#define __rw_yield(x)	barrier()
> > +#define SHARED_PROCESSOR	0
> > +#endif
> > +
> > +#ifdef CONFIG_QUEUED_SPINLOCKS
> > +#include <asm/qspinlock.h>
> > +#else
> >  static __always_inline int
> > arch_spin_value_unlocked(arch_spinlock_t
> > lock)
> >  {
> >  	return lock.slock == 0;
> > @@ -106,18 +120,6 @@ static inline int
> > arch_spin_trylock(arch_spinlock_t *lock)
> >   * held.  Conveniently, we have a word in the paca that holds this
> >   * value.
> >   */
> > -
> > -#if defined(CONFIG_PPC_SPLPAR)
> > -/* We only yield to the hypervisor if we are in shared processor
> > mode */
> > -#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca-
> > > 
> > > lppaca_ptr))
> > -extern void __spin_yield(arch_spinlock_t *lock);
> > -extern void __rw_yield(arch_rwlock_t *lock);
> > -#else /* SPLPAR */
> > -#define __spin_yield(x)	barrier()
> > -#define __rw_yield(x)	barrier()
> > -#define SHARED_PROCESSOR	0
> > -#endif
> > -
> >  static inline void arch_spin_lock(arch_spinlock_t *lock)
> >  {
> >  	CLEAR_IO_SYNC;
> > @@ -169,6 +171,7 @@ extern void
> > arch_spin_unlock_wait(arch_spinlock_t
> > *lock);
> >  	do { while (arch_spin_is_locked(lock)) cpu_relax(); }
> > while
> > (0)
> >  #endif
> >  
> > +#endif /* !CONFIG_QUEUED_SPINLOCKS */
> >  /*
> >   * Read-write spinlocks, allowing multiple readers
> >   * but only one writer.
> > diff --git a/arch/powerpc/include/asm/spinlock_types.h
> > b/arch/powerpc/include/asm/spinlock_types.h
> > index 2351adc..bd7144e 100644
> > --- a/arch/powerpc/include/asm/spinlock_types.h
> > +++ b/arch/powerpc/include/asm/spinlock_types.h
> > @@ -5,11 +5,15 @@
> >  # error "please don't include this file directly"
> >  #endif
> >  
> > +#ifdef CONFIG_QUEUED_SPINLOCKS
> > +#include <asm-generic/qspinlock_types.h>
> > +#else
> >  typedef struct {
> >  	volatile unsigned int slock;
> >  } arch_spinlock_t;
> >  
> >  #define __ARCH_SPIN_LOCK_UNLOCKED	{ 0 }
> > +#endif
> >  
> >  typedef struct {
> >  	volatile signed int lock;
> > diff --git a/arch/powerpc/lib/locks.c b/arch/powerpc/lib/locks.c
> > index f7deebd..a9ebd71 100644
> > --- a/arch/powerpc/lib/locks.c
> > +++ b/arch/powerpc/lib/locks.c
> > @@ -23,6 +23,7 @@
> >  #include <asm/hvcall.h>
> >  #include <asm/smp.h>
> >  
> > +#ifndef CONFIG_QUEUED_SPINLOCKS
> >  void __spin_yield(arch_spinlock_t *lock)
> >  {
> >  	unsigned int lock_value, holder_cpu, yield_count;
> > @@ -42,6 +43,7 @@ void __spin_yield(arch_spinlock_t *lock)
> >  		get_hard_smp_processor_id(holder_cpu),
> > yield_count);
> >  }
> >  EXPORT_SYMBOL_GPL(__spin_yield);
> > +#endif
> >  
> >  /*
> >   * Waiting for a read lock or a write lock on a rwlock...
> > @@ -69,6 +71,7 @@ void __rw_yield(arch_rwlock_t *rw)
> >  }
> >  #endif
> >  
> > +#ifndef CONFIG_QUEUED_SPINLOCKS
> >  void arch_spin_unlock_wait(arch_spinlock_t *lock)
> >  {
> >  	smp_mb();
> > @@ -84,3 +87,4 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock)
> >  }
> >  
> >  EXPORT_SYMBOL(arch_spin_unlock_wait);
> > +#endif