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s390: use generic rwsem implementation 

We never optimized our rwsem inline assemblies to make use of the new
atomic instructions. The generic rwsem implementation implicitly makes
use of the new instructions, since it implements the required rwsem
primitives with atomic operations, which we did optimize.

However even when compiling for old architectures the generic variant
still generates better code. So it's time to simply remove our old
code and switch to the generic implementation.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2017-09-30 10:54:31 +02:00 committed by Martin Schwidefsky
parent e0d281d067
commit 91a1fad759
2 changed files with 1 additions and 210 deletions
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1
arch/s390/include/asm/Kbuild
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@ -15,6 +15,7 @@ generic-y += local64.h
generic-y += mcs_spinlock.h
generic-y += mm-arch-hooks.h
generic-y += preempt.h
generic-y += rwsem.h
generic-y += trace_clock.h
generic-y += unaligned.h
generic-y += word-at-a-time.h

210
arch/s390/include/asm/rwsem.h
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@ -1,210 +0,0 @@
#ifndef _S390_RWSEM_H
#define _S390_RWSEM_H
/*
* S390 version
* Copyright IBM Corp. 2002
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
*
* Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
*/
/*
*
* The MSW of the count is the negated number of active writers and waiting
* lockers, and the LSW is the total number of active locks
*
* The lock count is initialized to 0 (no active and no waiting lockers).
*
* When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
* uncontended lock. This can be determined because XADD returns the old value.
* Readers increment by 1 and see a positive value when uncontended, negative
* if there are writers (and maybe) readers waiting (in which case it goes to
* sleep).
*
* The value of WAITING_BIAS supports up to 32766 waiting processes. This can
* be extended to 65534 by manually checking the whole MSW rather than relying
* on the S flag.
*
* The value of ACTIVE_BIAS supports up to 65535 active processes.
*
* This should be totally fair - if anything is waiting, a process that wants a
* lock will go to the back of the queue. When the currently active lock is
* released, if there's a writer at the front of the queue, then that and only
* that will be woken up; if there's a bunch of consecutive readers at the
* front, then they'll all be woken up, but no other readers will be.
*/
#ifndef _LINUX_RWSEM_H
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
#endif
#define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
#define RWSEM_ACTIVE_BIAS 0x0000000000000001L
#define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
#define RWSEM_WAITING_BIAS (-0x0000000100000000L)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
/*
* lock for reading
*/
static inline void __down_read(struct rw_semaphore *sem)
{
signed long old, new;
asm volatile(
" lg %0,%2\n"
"0: lgr %1,%0\n"
" aghi %1,%4\n"
" csg %0,%1,%2\n"
" jl 0b"
: "=&d" (old), "=&d" (new), "=Q" (sem->count)
: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
: "cc", "memory");
if (old < 0)
rwsem_down_read_failed(sem);
}
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
signed long old, new;
asm volatile(
" lg %0,%2\n"
"0: ltgr %1,%0\n"
" jm 1f\n"
" aghi %1,%4\n"
" csg %0,%1,%2\n"
" jl 0b\n"
"1:"
: "=&d" (old), "=&d" (new), "=Q" (sem->count)
: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)
: "cc", "memory");
return old >= 0 ? 1 : 0;
}
/*
* lock for writing
*/
static inline long ___down_write(struct rw_semaphore *sem)
{
signed long old, new, tmp;
tmp = RWSEM_ACTIVE_WRITE_BIAS;
asm volatile(
" lg %0,%2\n"
"0: lgr %1,%0\n"
" ag %1,%4\n"
" csg %0,%1,%2\n"
" jl 0b"
: "=&d" (old), "=&d" (new), "=Q" (sem->count)
: "Q" (sem->count), "m" (tmp)
: "cc", "memory");
return old;
}
static inline void __down_write(struct rw_semaphore *sem)
{
if (___down_write(sem))
rwsem_down_write_failed(sem);
}
static inline int __down_write_killable(struct rw_semaphore *sem)
{
if (___down_write(sem))
if (IS_ERR(rwsem_down_write_failed_killable(sem)))
return -EINTR;
return 0;
}
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
signed long old;
asm volatile(
" lg %0,%1\n"
"0: ltgr %0,%0\n"
" jnz 1f\n"
" csg %0,%3,%1\n"
" jl 0b\n"
"1:"
: "=&d" (old), "=Q" (sem->count)
: "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS)
: "cc", "memory");
return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;
}
/*
* unlock after reading
*/
static inline void __up_read(struct rw_semaphore *sem)
{
signed long old, new;
asm volatile(
" lg %0,%2\n"
"0: lgr %1,%0\n"
" aghi %1,%4\n"
" csg %0,%1,%2\n"
" jl 0b"
: "=&d" (old), "=&d" (new), "=Q" (sem->count)
: "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS)
: "cc", "memory");
if (new < 0)
if ((new & RWSEM_ACTIVE_MASK) == 0)
rwsem_wake(sem);
}
/*
* unlock after writing
*/
static inline void __up_write(struct rw_semaphore *sem)
{
signed long old, new, tmp;
tmp = -RWSEM_ACTIVE_WRITE_BIAS;
asm volatile(
" lg %0,%2\n"
"0: lgr %1,%0\n"
" ag %1,%4\n"
" csg %0,%1,%2\n"
" jl 0b"
: "=&d" (old), "=&d" (new), "=Q" (sem->count)
: "Q" (sem->count), "m" (tmp)
: "cc", "memory");
if (new < 0)
if ((new & RWSEM_ACTIVE_MASK) == 0)
rwsem_wake(sem);
}
/*
* downgrade write lock to read lock
*/
static inline void __downgrade_write(struct rw_semaphore *sem)
{
signed long old, new, tmp;
tmp = -RWSEM_WAITING_BIAS;
asm volatile(
" lg %0,%2\n"
"0: lgr %1,%0\n"
" ag %1,%4\n"
" csg %0,%1,%2\n"
" jl 0b"
: "=&d" (old), "=&d" (new), "=Q" (sem->count)
: "Q" (sem->count), "m" (tmp)
: "cc", "memory");
if (new > 1)
rwsem_downgrade_wake(sem);
}
#endif /* _S390_RWSEM_H */