From 2c72a44ecdf2a7ceac73844226e97ed2d5dd1e82 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Wed, 14 Jan 2015 17:52:33 +0100 Subject: [PATCH] s390/spinlock: add compare-and-delay to lock wait loops Add the compare-and-delay instruction to the spin-lock and rw-lock retry loops. A CPU executing the compare-and-delay instruction stops until the lock value has changed. This is done to make the locking code for contended locks to behave better in regard to the multi- hreading facility. A thread of a core executing a compare-and-delay will allow the other threads of a core to get a larger share of the core resources. Signed-off-by: Martin Schwidefsky --- arch/s390/include/asm/setup.h | 3 ++ arch/s390/kernel/early.c | 18 ++++++++++++ arch/s390/lib/spinlock.c | 52 ++++++++++++++++++++++++++++++----- 3 files changed, 66 insertions(+), 7 deletions(-) diff --git a/arch/s390/include/asm/setup.h b/arch/s390/include/asm/setup.h index 7736fdd72595..b8d1e54b4733 100644 --- a/arch/s390/include/asm/setup.h +++ b/arch/s390/include/asm/setup.h @@ -57,6 +57,7 @@ extern void detect_memory_memblock(void); #define MACHINE_FLAG_TE (1UL << 15) #define MACHINE_FLAG_TLB_LC (1UL << 17) #define MACHINE_FLAG_VX (1UL << 18) +#define MACHINE_FLAG_CAD (1UL << 19) #define MACHINE_IS_VM (S390_lowcore.machine_flags & MACHINE_FLAG_VM) #define MACHINE_IS_KVM (S390_lowcore.machine_flags & MACHINE_FLAG_KVM) @@ -80,6 +81,7 @@ extern void detect_memory_memblock(void); #define MACHINE_HAS_TE (0) #define MACHINE_HAS_TLB_LC (0) #define MACHINE_HAS_VX (0) +#define MACHINE_HAS_CAD (0) #else /* CONFIG_64BIT */ #define MACHINE_HAS_IEEE (1) #define MACHINE_HAS_CSP (1) @@ -93,6 +95,7 @@ extern void detect_memory_memblock(void); #define MACHINE_HAS_TE (S390_lowcore.machine_flags & MACHINE_FLAG_TE) #define MACHINE_HAS_TLB_LC (S390_lowcore.machine_flags & MACHINE_FLAG_TLB_LC) #define MACHINE_HAS_VX (S390_lowcore.machine_flags & MACHINE_FLAG_VX) +#define MACHINE_HAS_CAD (S390_lowcore.machine_flags & MACHINE_FLAG_CAD) #endif /* CONFIG_64BIT */ /* diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c index 302ac1f7f8e7..70a329450901 100644 --- a/arch/s390/kernel/early.c +++ b/arch/s390/kernel/early.c @@ -393,9 +393,27 @@ static __init void detect_machine_facilities(void) S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_LC; if (test_facility(129)) S390_lowcore.machine_flags |= MACHINE_FLAG_VX; + if (test_facility(128)) + S390_lowcore.machine_flags |= MACHINE_FLAG_CAD; #endif } +static int __init nocad_setup(char *str) +{ + S390_lowcore.machine_flags &= ~MACHINE_FLAG_CAD; + return 0; +} +early_param("nocad", nocad_setup); + +static int __init cad_init(void) +{ + if (MACHINE_HAS_CAD) + /* Enable problem state CAD. */ + __ctl_set_bit(2, 3); + return 0; +} +early_initcall(cad_init); + static __init void rescue_initrd(void) { #ifdef CONFIG_BLK_DEV_INITRD diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c index 034a35a3e9c1..d6c9991f7797 100644 --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -12,7 +12,15 @@ #include #include -int spin_retry = 1000; +int spin_retry = -1; + +static int __init spin_retry_init(void) +{ + if (spin_retry < 0) + spin_retry = MACHINE_HAS_CAD ? 10 : 1000; + return 0; +} +early_initcall(spin_retry_init); /** * spin_retry= parameter @@ -24,6 +32,11 @@ static int __init spin_retry_setup(char *str) } __setup("spin_retry=", spin_retry_setup); +static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old) +{ + asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock)); +} + void arch_spin_lock_wait(arch_spinlock_t *lp) { unsigned int cpu = SPINLOCK_LOCKVAL; @@ -46,6 +59,8 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) /* Loop for a while on the lock value. */ count = spin_retry; do { + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&lp->lock, owner); owner = ACCESS_ONCE(lp->lock); } while (owner && count-- > 0); if (!owner) @@ -84,6 +99,8 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) /* Loop for a while on the lock value. */ count = spin_retry; do { + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&lp->lock, owner); owner = ACCESS_ONCE(lp->lock); } while (owner && count-- > 0); if (!owner) @@ -100,11 +117,19 @@ EXPORT_SYMBOL(arch_spin_lock_wait_flags); int arch_spin_trylock_retry(arch_spinlock_t *lp) { + unsigned int cpu = SPINLOCK_LOCKVAL; + unsigned int owner; int count; - for (count = spin_retry; count > 0; count--) - if (arch_spin_trylock_once(lp)) - return 1; + for (count = spin_retry; count > 0; count--) { + owner = ACCESS_ONCE(lp->lock); + /* Try to get the lock if it is free. */ + if (!owner) { + if (_raw_compare_and_swap(&lp->lock, 0, cpu)) + return 1; + } else if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&lp->lock, owner); + } return 0; } EXPORT_SYMBOL(arch_spin_trylock_retry); @@ -126,8 +151,11 @@ void _raw_read_lock_wait(arch_rwlock_t *rw) } old = ACCESS_ONCE(rw->lock); owner = ACCESS_ONCE(rw->owner); - if ((int) old < 0) + if ((int) old < 0) { + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&rw->lock, old); continue; + } if (_raw_compare_and_swap(&rw->lock, old, old + 1)) return; } @@ -141,8 +169,11 @@ int _raw_read_trylock_retry(arch_rwlock_t *rw) while (count-- > 0) { old = ACCESS_ONCE(rw->lock); - if ((int) old < 0) + if ((int) old < 0) { + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&rw->lock, old); continue; + } if (_raw_compare_and_swap(&rw->lock, old, old + 1)) return 1; } @@ -173,6 +204,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev) } if ((old & 0x7fffffff) == 0 && (int) prev >= 0) break; + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&rw->lock, old); } } EXPORT_SYMBOL(_raw_write_lock_wait); @@ -201,6 +234,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw) smp_rmb(); if ((old & 0x7fffffff) == 0 && (int) prev >= 0) break; + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&rw->lock, old); } } EXPORT_SYMBOL(_raw_write_lock_wait); @@ -214,8 +249,11 @@ int _raw_write_trylock_retry(arch_rwlock_t *rw) while (count-- > 0) { old = ACCESS_ONCE(rw->lock); - if (old) + if (old) { + if (MACHINE_HAS_CAD) + _raw_compare_and_delay(&rw->lock, old); continue; + } if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000)) return 1; } -- 2.20.1