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Message-ID: <20160517110906.GW3193@twins.programming.kicks-ass.net>
Date: Tue, 17 May 2016 13:09:06 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Jason Low <jason.low2@....com>, Ingo Molnar <mingo@...hat.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Richard Henderson <rth@...ddle.net>,
Ivan Kokshaysky <ink@...assic.park.msu.ru>,
Matt Turner <mattst88@...il.com>,
Tony Luck <tony.luck@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Terry Rudd <terry.rudd@....com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Arnd Bergmann <arnd@...db.de>,
Christoph Lameter <cl@...ux.com>,
Davidlohr Bueso <dave@...olabs.net>,
Waiman Long <Waiman.Long@....com>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Peter Hurley <peter@...leysoftware.com>,
Jason Low <jason.low2@...com>
Subject: Re: [RFC][PATCH 0/7] locking/rwsem: Convert rwsem count to
atomic_long_t
On Mon, May 16, 2016 at 06:12:25PM -0700, Linus Torvalds wrote:
> On Mon, May 16, 2016 at 5:37 PM, Jason Low <jason.low2@....com> wrote:
> >
> > This rest of the series converts the rwsem count variable to an atomic_long_t
> > since it is used it as an atomic variable. This allows us to also remove
> > the rwsem_atomic_{add,update} abstraction and reduce 100+ lines of code.
>
> I would suggest you merge all the "remove rwsem_atomic_{add,update}"
> patches into a single patch.
>
> I don't see the advantage to splitting those up by architecture, and
> it does add noise to the series.
>
> Other than that it all looks fine to me.
OK, done.
---
Subject: locking,rwsem: Remove rwsem_atomic_add() and rwsem_atomic_update()
From: Jason Low <jason.low2@....com>
Date: Mon, 16 May 2016 17:38:02 -0700
The rwsem-xadd count has been converted to an atomic variable and the
rwsem code now directly uses atomic_long_add() and
atomic_long_add_return(), so we can remove the arch implementations of
rwsem_atomic_add() and rwsem_atomic_update().
Cc: Waiman Long <Waiman.Long@....com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Jason Low <jason.low2@...com>
Cc: Richard Henderson <rth@...ddle.net>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Terry Rudd <terry.rudd@....com>
Cc: Peter Hurley <peter@...leysoftware.com>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Ivan Kokshaysky <ink@...assic.park.msu.ru>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Matt Turner <mattst88@...il.com>
Signed-off-by: Jason Low <jason.low2@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
arch/alpha/include/asm/rwsem.h | 42 -----------------------------------------
arch/ia64/include/asm/rwsem.h | 7 ------
arch/s390/include/asm/rwsem.h | 37 ------------------------------------
arch/x86/include/asm/rwsem.h | 18 -----------------
include/asm-generic/rwsem.h | 16 ---------------
5 files changed, 120 deletions(-)
--- a/arch/alpha/include/asm/rwsem.h
+++ b/arch/alpha/include/asm/rwsem.h
@@ -191,47 +191,5 @@ static inline void __downgrade_write(str
rwsem_downgrade_wake(sem);
}
-static inline void rwsem_atomic_add(long val, struct rw_semaphore *sem)
-{
-#ifndef CONFIG_SMP
- sem->count += val;
-#else
- long temp;
- __asm__ __volatile__(
- "1: ldq_l %0,%1\n"
- " addq %0,%2,%0\n"
- " stq_c %0,%1\n"
- " beq %0,2f\n"
- ".subsection 2\n"
- "2: br 1b\n"
- ".previous"
- :"=&r" (temp), "=m" (sem->count)
- :"Ir" (val), "m" (sem->count));
-#endif
-}
-
-static inline long rwsem_atomic_update(long val, struct rw_semaphore *sem)
-{
-#ifndef CONFIG_SMP
- sem->count += val;
- return sem->count;
-#else
- long ret, temp;
- __asm__ __volatile__(
- "1: ldq_l %0,%1\n"
- " addq %0,%3,%2\n"
- " addq %0,%3,%0\n"
- " stq_c %2,%1\n"
- " beq %2,2f\n"
- ".subsection 2\n"
- "2: br 1b\n"
- ".previous"
- :"=&r" (ret), "=m" (sem->count), "=&r" (temp)
- :"Ir" (val), "m" (sem->count));
-
- return ret;
-#endif
-}
-
#endif /* __KERNEL__ */
#endif /* _ALPHA_RWSEM_H */
--- a/arch/ia64/include/asm/rwsem.h
+++ b/arch/ia64/include/asm/rwsem.h
@@ -151,11 +151,4 @@ __downgrade_write (struct rw_semaphore *
rwsem_downgrade_wake(sem);
}
-/*
- * Implement atomic add functionality. These used to be "inline" functions, but GCC v3.1
- * doesn't quite optimize this stuff right and ends up with bad calls to fetchandadd.
- */
-#define rwsem_atomic_add(delta, sem) atomic64_add(delta, (atomic64_t *)(&(sem)->count))
-#define rwsem_atomic_update(delta, sem) atomic64_add_return(delta, (atomic64_t *)(&(sem)->count))
-
#endif /* _ASM_IA64_RWSEM_H */
--- a/arch/s390/include/asm/rwsem.h
+++ b/arch/s390/include/asm/rwsem.h
@@ -207,41 +207,4 @@ static inline void __downgrade_write(str
rwsem_downgrade_wake(sem);
}
-/*
- * implement atomic add functionality
- */
-static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
-{
- signed long old, new;
-
- asm volatile(
- " lg %0,%2\n"
- "0: lgr %1,%0\n"
- " agr %1,%4\n"
- " csg %0,%1,%2\n"
- " jl 0b"
- : "=&d" (old), "=&d" (new), "=Q" (sem->count)
- : "Q" (sem->count), "d" (delta)
- : "cc", "memory");
-}
-
-/*
- * implement exchange and add functionality
- */
-static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
-{
- signed long old, new;
-
- asm volatile(
- " lg %0,%2\n"
- "0: lgr %1,%0\n"
- " agr %1,%4\n"
- " csg %0,%1,%2\n"
- " jl 0b"
- : "=&d" (old), "=&d" (new), "=Q" (sem->count)
- : "Q" (sem->count), "d" (delta)
- : "cc", "memory");
- return new;
-}
-
#endif /* _S390_RWSEM_H */
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -215,23 +215,5 @@ static inline void __downgrade_write(str
: "memory", "cc");
}
-/*
- * implement atomic add functionality
- */
-static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
-{
- asm volatile(LOCK_PREFIX _ASM_ADD "%1,%0"
- : "+m" (sem->count)
- : "er" (delta));
-}
-
-/*
- * implement exchange and add functionality
- */
-static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
-{
- return delta + xadd(&sem->count, delta);
-}
-
#endif /* __KERNEL__ */
#endif /* _ASM_X86_RWSEM_H */
--- a/include/asm-generic/rwsem.h
+++ b/include/asm-generic/rwsem.h
@@ -107,14 +107,6 @@ static inline void __up_write(struct rw_
}
/*
- * implement atomic add functionality
- */
-static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
-{
- atomic_long_add(delta, (atomic_long_t *)&sem->count);
-}
-
-/*
* downgrade write lock to read lock
*/
static inline void __downgrade_write(struct rw_semaphore *sem)
@@ -134,13 +126,5 @@ static inline void __downgrade_write(str
rwsem_downgrade_wake(sem);
}
-/*
- * implement exchange and add functionality
- */
-static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
-{
- return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
-}
-
#endif /* __KERNEL__ */
#endif /* _ASM_GENERIC_RWSEM_H */
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