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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 01:10:04 +00:00
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 <schwidefsky@de.ibm.com>
This commit is contained in:
parent
55b5eb75e7
commit
2c72a44ecd
3 changed files with 66 additions and 7 deletions
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@ -57,6 +57,7 @@ extern void detect_memory_memblock(void);
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#define MACHINE_FLAG_TE (1UL << 15)
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#define MACHINE_FLAG_TLB_LC (1UL << 17)
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#define MACHINE_FLAG_VX (1UL << 18)
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#define MACHINE_FLAG_CAD (1UL << 19)
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#define MACHINE_IS_VM (S390_lowcore.machine_flags & MACHINE_FLAG_VM)
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#define MACHINE_IS_KVM (S390_lowcore.machine_flags & MACHINE_FLAG_KVM)
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@ -80,6 +81,7 @@ extern void detect_memory_memblock(void);
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#define MACHINE_HAS_TE (0)
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#define MACHINE_HAS_TLB_LC (0)
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#define MACHINE_HAS_VX (0)
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#define MACHINE_HAS_CAD (0)
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#else /* CONFIG_64BIT */
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#define MACHINE_HAS_IEEE (1)
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#define MACHINE_HAS_CSP (1)
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@ -93,6 +95,7 @@ extern void detect_memory_memblock(void);
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#define MACHINE_HAS_TE (S390_lowcore.machine_flags & MACHINE_FLAG_TE)
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#define MACHINE_HAS_TLB_LC (S390_lowcore.machine_flags & MACHINE_FLAG_TLB_LC)
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#define MACHINE_HAS_VX (S390_lowcore.machine_flags & MACHINE_FLAG_VX)
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#define MACHINE_HAS_CAD (S390_lowcore.machine_flags & MACHINE_FLAG_CAD)
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#endif /* CONFIG_64BIT */
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/*
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@ -393,9 +393,27 @@ static __init void detect_machine_facilities(void)
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S390_lowcore.machine_flags |= MACHINE_FLAG_TLB_LC;
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if (test_facility(129))
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S390_lowcore.machine_flags |= MACHINE_FLAG_VX;
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if (test_facility(128))
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S390_lowcore.machine_flags |= MACHINE_FLAG_CAD;
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#endif
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}
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static int __init nocad_setup(char *str)
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{
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S390_lowcore.machine_flags &= ~MACHINE_FLAG_CAD;
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return 0;
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}
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early_param("nocad", nocad_setup);
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static int __init cad_init(void)
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{
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if (MACHINE_HAS_CAD)
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/* Enable problem state CAD. */
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__ctl_set_bit(2, 3);
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return 0;
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}
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early_initcall(cad_init);
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static __init void rescue_initrd(void)
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{
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#ifdef CONFIG_BLK_DEV_INITRD
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@ -12,7 +12,15 @@
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#include <linux/smp.h>
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#include <asm/io.h>
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int spin_retry = 1000;
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int spin_retry = -1;
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static int __init spin_retry_init(void)
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{
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if (spin_retry < 0)
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spin_retry = MACHINE_HAS_CAD ? 10 : 1000;
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return 0;
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}
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early_initcall(spin_retry_init);
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/**
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* spin_retry= parameter
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@ -24,6 +32,11 @@ static int __init spin_retry_setup(char *str)
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}
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__setup("spin_retry=", spin_retry_setup);
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static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
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{
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asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
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}
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void arch_spin_lock_wait(arch_spinlock_t *lp)
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{
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unsigned int cpu = SPINLOCK_LOCKVAL;
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@ -46,6 +59,8 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
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/* Loop for a while on the lock value. */
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count = spin_retry;
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do {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&lp->lock, owner);
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owner = ACCESS_ONCE(lp->lock);
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} while (owner && count-- > 0);
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if (!owner)
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@ -84,6 +99,8 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
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/* Loop for a while on the lock value. */
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count = spin_retry;
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do {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&lp->lock, owner);
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owner = ACCESS_ONCE(lp->lock);
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} while (owner && count-- > 0);
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if (!owner)
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@ -100,11 +117,19 @@ EXPORT_SYMBOL(arch_spin_lock_wait_flags);
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int arch_spin_trylock_retry(arch_spinlock_t *lp)
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{
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unsigned int cpu = SPINLOCK_LOCKVAL;
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unsigned int owner;
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int count;
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for (count = spin_retry; count > 0; count--)
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if (arch_spin_trylock_once(lp))
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return 1;
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for (count = spin_retry; count > 0; count--) {
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owner = ACCESS_ONCE(lp->lock);
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/* Try to get the lock if it is free. */
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if (!owner) {
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if (_raw_compare_and_swap(&lp->lock, 0, cpu))
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return 1;
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} else if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&lp->lock, owner);
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}
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return 0;
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}
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EXPORT_SYMBOL(arch_spin_trylock_retry);
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@ -126,8 +151,11 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
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}
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old = ACCESS_ONCE(rw->lock);
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owner = ACCESS_ONCE(rw->owner);
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if ((int) old < 0)
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if ((int) old < 0) {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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continue;
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}
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if (_raw_compare_and_swap(&rw->lock, old, old + 1))
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return;
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}
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@ -141,8 +169,11 @@ int _raw_read_trylock_retry(arch_rwlock_t *rw)
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while (count-- > 0) {
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old = ACCESS_ONCE(rw->lock);
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if ((int) old < 0)
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if ((int) old < 0) {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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continue;
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}
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if (_raw_compare_and_swap(&rw->lock, old, old + 1))
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return 1;
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}
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@ -173,6 +204,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
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}
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if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
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break;
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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}
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}
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EXPORT_SYMBOL(_raw_write_lock_wait);
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@ -201,6 +234,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
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smp_rmb();
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if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
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break;
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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}
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}
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EXPORT_SYMBOL(_raw_write_lock_wait);
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@ -214,8 +249,11 @@ int _raw_write_trylock_retry(arch_rwlock_t *rw)
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while (count-- > 0) {
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old = ACCESS_ONCE(rw->lock);
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if (old)
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if (old) {
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if (MACHINE_HAS_CAD)
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_raw_compare_and_delay(&rw->lock, old);
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continue;
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}
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if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))
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return 1;
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}
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