Commit 59b69787 authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Martin Schwidefsky
Browse files

[S390] spinlock: check virtual cpu running status 



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: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 8387c736

arch/s390/include/asm/sigp.h

+19 −21
Original line number Diff line number Diff line
@@ -25,29 +25,28 @@ static inline int cpu_logical_map(int cpu) 
}



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,

};



enum {

	sigp_order_code_accepted = 0,

	sigp_status_stored,

	sigp_busy,

	sigp_not_operational

	sigp_status_stored = 1,

	sigp_busy = 2,

	sigp_not_operational = 3,

};



/*
@@ -57,7 +56,6 @@ enum { 
	ec_schedule = 0,

	ec_call_function,

	ec_call_function_single,

	ec_bit_last

};



/*

arch/s390/include/asm/smp.h

+24 −0
Original line number Diff line number Diff line
@@ -36,6 +36,28 @@ extern void smp_switch_to_cpu(void (*)(void *), void *, unsigned long sp, 
			      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;



	switch (sigp_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 @@ static inline void smp_switch_to_ipl_cpu(void (*func)(void *), void *data) 
	func(data);

}



#define smp_vcpu_scheduled	(1)



#endif /* CONFIG_SMP */



#ifdef CONFIG_HOTPLUG_CPU

arch/s390/lib/spinlock.c

+37 −16
Original line number Diff line number Diff line
@@ -43,16 +43,24 @@ void arch_spin_lock_wait(arch_spinlock_t *lp) 
{

	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;

		}

		owner = lp->owner_cpu;

		if (owner)

			_raw_yield_cpu(~owner);

		if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)

			return;

	}
@@ -63,18 +71,28 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags) 
{

	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;

		}

		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;

		local_irq_restore(flags);
@@ -100,9 +118,12 @@ EXPORT_SYMBOL(arch_spin_trylock_retry); 
void arch_spin_relax(arch_spinlock_t *lock)

{

	unsigned int cpu = lock->owner_cpu;

	if (cpu != 0)

	if (cpu != 0) {

		if (MACHINE_IS_VM || MACHINE_IS_KVM ||

		    !smp_vcpu_scheduled(~cpu))

			_raw_yield_cpu(~cpu);

	}

}

EXPORT_SYMBOL(arch_spin_relax);



void _raw_read_lock_wait(arch_rwlock_t *rw)

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