From: Gerald Schaefer This patch introduces a new function that checks the running status of a cpu in a hypervisor. This status is not virtualized, so the check is only correct if running in an LPAR. On acquiring a spinlock, if the cpu holding the lock is scheduled by the hypervisor, we do a busy wait on the lock. If it is not scheduled, we yield over to that cpu. Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky --- arch/s390/include/asm/sigp.h | 40 ++++++++++++++---------------- arch/s390/include/asm/smp.h | 24 ++++++++++++++++++ arch/s390/lib/spinlock.c | 57 +++++++++++++++++++++++++++++-------------- 3 files changed, 82 insertions(+), 39 deletions(-) Index: quilt-2.6/arch/s390/include/asm/sigp.h =================================================================== --- quilt-2.6.orig/arch/s390/include/asm/sigp.h 2010-02-24 09:28:13.000000000 +0100 +++ quilt-2.6/arch/s390/include/asm/sigp.h 2010-02-24 09:44:25.000000000 +0100 @@ -31,32 +31,31 @@ typedef enum { - sigp_unassigned=0x0, - sigp_sense, - sigp_external_call, - sigp_emergency_signal, - sigp_start, - sigp_stop, - sigp_restart, - sigp_unassigned1, - sigp_unassigned2, - sigp_stop_and_store_status, - sigp_unassigned3, - sigp_initial_cpu_reset, - sigp_cpu_reset, - sigp_set_prefix, - sigp_store_status_at_address, - sigp_store_extended_status_at_address + sigp_sense = 1, + sigp_external_call = 2, + sigp_emergency_signal = 3, + sigp_start = 4, + sigp_stop = 5, + sigp_restart = 6, + sigp_stop_and_store_status = 9, + sigp_initial_cpu_reset = 11, + sigp_cpu_reset = 12, + sigp_set_prefix = 13, + sigp_store_status_at_address = 14, + sigp_store_extended_status_at_address = 15, + sigp_set_architecture = 18, + sigp_conditional_emergency_signal = 19, + sigp_sense_running = 21, } sigp_order_code; typedef __u32 sigp_status_word; typedef enum { - sigp_order_code_accepted=0, - sigp_status_stored, - sigp_busy, - sigp_not_operational + sigp_order_code_accepted = 0, + sigp_status_stored = 1, + sigp_busy = 2, + sigp_not_operational = 3, } sigp_ccode; @@ -70,7 +69,6 @@ ec_schedule=0, ec_call_function, ec_call_function_single, - ec_bit_last } ec_bit_sig; /* Index: quilt-2.6/arch/s390/include/asm/smp.h =================================================================== --- quilt-2.6.orig/arch/s390/include/asm/smp.h 2010-02-24 09:44:24.000000000 +0100 +++ quilt-2.6/arch/s390/include/asm/smp.h 2010-02-24 09:44:25.000000000 +0100 @@ -36,6 +36,28 @@ int from, int to); extern void smp_restart_cpu(void); +/* + * returns 1 if (virtual) cpu is scheduled + * returns 0 otherwise + */ +static inline int smp_vcpu_scheduled(int cpu) +{ + __u32 status = 0; + + switch (signal_processor_ps(&status, 0, cpu, sigp_sense_running)) { + case sigp_status_stored: + /* Check for running status */ + if (status & 0x400) + return 0; + break; + case sigp_not_operational: + return 0; + default: + break; + } + return 1; +} + #else /* CONFIG_SMP */ static inline void smp_switch_to_ipl_cpu(void (*func)(void *), void *data) @@ -43,6 +65,8 @@ func(data); } +#define smp_vcpu_scheduled (1) + #endif /* CONFIG_SMP */ #ifdef CONFIG_HOTPLUG_CPU Index: quilt-2.6/arch/s390/lib/spinlock.c =================================================================== --- quilt-2.6.orig/arch/s390/lib/spinlock.c 2010-02-24 09:28:13.000000000 +0100 +++ quilt-2.6/arch/s390/lib/spinlock.c 2010-02-24 09:44:25.000000000 +0100 @@ -43,16 +43,24 @@ { int count = spin_retry; unsigned int cpu = ~smp_processor_id(); + unsigned int owner; while (1) { - if (count-- <= 0) { - unsigned int owner = lp->owner_cpu; - if (owner != 0) - _raw_yield_cpu(~owner); - count = spin_retry; + owner = lp->owner_cpu; + if (!owner || smp_vcpu_scheduled(~owner)) { + for (count = spin_retry; count > 0; count--) { + if (arch_spin_is_locked(lp)) + continue; + if (_raw_compare_and_swap(&lp->owner_cpu, 0, + cpu) == 0) + return; + } + if (MACHINE_IS_LPAR) + continue; } - if (arch_spin_is_locked(lp)) - continue; + owner = lp->owner_cpu; + if (owner) + _raw_yield_cpu(~owner); if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0) return; } @@ -63,17 +71,27 @@ { int count = spin_retry; unsigned int cpu = ~smp_processor_id(); + unsigned int owner; local_irq_restore(flags); while (1) { - if (count-- <= 0) { - unsigned int owner = lp->owner_cpu; - if (owner != 0) - _raw_yield_cpu(~owner); - count = spin_retry; + owner = lp->owner_cpu; + if (!owner || smp_vcpu_scheduled(~owner)) { + for (count = spin_retry; count > 0; count--) { + if (arch_spin_is_locked(lp)) + continue; + local_irq_disable(); + if (_raw_compare_and_swap(&lp->owner_cpu, 0, + cpu) == 0) + return; + local_irq_restore(flags); + } + if (MACHINE_IS_LPAR) + continue; } - if (arch_spin_is_locked(lp)) - continue; + owner = lp->owner_cpu; + if (owner) + _raw_yield_cpu(~owner); local_irq_disable(); if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0) return; @@ -100,8 +118,11 @@ void arch_spin_relax(arch_spinlock_t *lock) { unsigned int cpu = lock->owner_cpu; - if (cpu != 0) - _raw_yield_cpu(~cpu); + if (cpu != 0) { + if (MACHINE_IS_VM || MACHINE_IS_KVM || + !smp_vcpu_scheduled(~cpu)) + _raw_yield_cpu(~cpu); + } } EXPORT_SYMBOL(arch_spin_relax); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/