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Date: Fri, 03 Jun 2016 11:32:00 +1000
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.orgv,
virtualization@...ts.linux-foundation.org
Cc: paulus@...ba.org, mpe@...erman.id.au, peterz@...radead.org,
mingo@...hat.com, paulmck@...ux.vnet.ibm.com, waiman.long@....com
Subject: Re: [PATCH v5 1/6] qspinlock: powerpc support qspinlock
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@...ux.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
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