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Date: Fri, 03 Jun 2016 11:32:28 +1000
From: Benjamin Herrenschmidt <benh@....ibm.com>
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 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@...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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