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
......@@ -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_order_code_accepted = 0,
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
};
/*
......
......@@ -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
......
......@@ -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;
}
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 @@ 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;
}
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 @@ EXPORT_SYMBOL(arch_spin_trylock_retry);
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);
......
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