From 951f22d5b1f0eaae35dafc669e3774a0c2084d10 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Wed, 27 Jul 2005 11:44:57 -0700 Subject: [PATCH] s390: spin lock retry Split spin lock and r/w lock implementation into a single try which is done inline and an out of line function that repeatedly tries to get the lock before doing the cpu_relax(). Add a system control to set the number of retries before a cpu is yielded. The reason for the spin lock retry is that the diagnose 0x44 that is used to give up the virtual cpu is quite expensive. For spin locks that are held only for a short period of time the costs of the diagnoses outweights the savings for spin locks that are held for a longer timer. The default retry count is 1000. Signed-off-by: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/s390/lib/spinlock.c | 133 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 arch/s390/lib/spinlock.c (limited to 'arch/s390/lib/spinlock.c') diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c new file mode 100644 index 00000000000..888b5596c19 --- /dev/null +++ b/arch/s390/lib/spinlock.c @@ -0,0 +1,133 @@ +/* + * arch/s390/lib/spinlock.c + * Out of line spinlock code. + * + * S390 version + * Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation + * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) + */ + +#include +#include +#include +#include +#include + +atomic_t spin_retry_counter; +int spin_retry = 1000; + +/** + * spin_retry= parameter + */ +static int __init spin_retry_setup(char *str) +{ + spin_retry = simple_strtoul(str, &str, 0); + return 1; +} +__setup("spin_retry=", spin_retry_setup); + +static inline void +_diag44(void) +{ +#ifdef __s390x__ + if (MACHINE_HAS_DIAG44) +#endif + asm volatile("diag 0,0,0x44"); +} + +void +_raw_spin_lock_wait(spinlock_t *lp, unsigned int pc) +{ + int count = spin_retry; + + while (1) { + if (count-- <= 0) { + _diag44(); + count = spin_retry; + } + atomic_inc(&spin_retry_counter); + if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0) + return; + } +} +EXPORT_SYMBOL(_raw_spin_lock_wait); + +int +_raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc) +{ + int count = spin_retry; + + while (count-- > 0) { + atomic_inc(&spin_retry_counter); + if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0) + return 1; + } + return 0; +} +EXPORT_SYMBOL(_raw_spin_trylock_retry); + +void +_raw_read_lock_wait(rwlock_t *rw) +{ + unsigned int old; + int count = spin_retry; + + while (1) { + if (count-- <= 0) { + _diag44(); + count = spin_retry; + } + atomic_inc(&spin_retry_counter); + old = rw->lock & 0x7fffffffU; + if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old) + return; + } +} +EXPORT_SYMBOL(_raw_read_lock_wait); + +int +_raw_read_trylock_retry(rwlock_t *rw) +{ + unsigned int old; + int count = spin_retry; + + while (count-- > 0) { + atomic_inc(&spin_retry_counter); + old = rw->lock & 0x7fffffffU; + if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old) + return 1; + } + return 0; +} +EXPORT_SYMBOL(_raw_read_trylock_retry); + +void +_raw_write_lock_wait(rwlock_t *rw) +{ + int count = spin_retry; + + while (1) { + if (count-- <= 0) { + _diag44(); + count = spin_retry; + } + atomic_inc(&spin_retry_counter); + if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0) + return; + } +} +EXPORT_SYMBOL(_raw_write_lock_wait); + +int +_raw_write_trylock_retry(rwlock_t *rw) +{ + int count = spin_retry; + + while (count-- > 0) { + atomic_inc(&spin_retry_counter); + if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0) + return 1; + } + return 0; +} +EXPORT_SYMBOL(_raw_write_trylock_retry); -- cgit v1.2.3