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

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

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.

> 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