From f0d733942750c1ee6358c3a4a1a5d7ba73b7122f Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 16 Oct 2007 11:51:30 -0700 Subject: xen: yield to IPI target if necessary When sending a call-function IPI to a vcpu, yield if the vcpu isn't running. Signed-off-by: Jeremy Fitzhardinge --- arch/x86/xen/smp.c | 14 ++++++++++---- arch/x86/xen/time.c | 6 ++++++ arch/x86/xen/xen-ops.h | 2 ++ 3 files changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 557b8e24706a..865953e6f341 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -360,7 +360,8 @@ int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *), void *info, int wait) { struct call_data_struct data; - int cpus; + int cpus, cpu; + bool yield; /* Holding any lock stops cpus from going down. */ spin_lock(&call_lock); @@ -389,9 +390,14 @@ int xen_smp_call_function_mask(cpumask_t mask, void (*func)(void *), /* Send a message to other CPUs and wait for them to respond */ xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR); - /* Make sure other vcpus get a chance to run. - XXX too severe? Maybe we should check the other CPU's states? */ - HYPERVISOR_sched_op(SCHEDOP_yield, 0); + /* Make sure other vcpus get a chance to run if they need to. */ + yield = false; + for_each_cpu_mask(cpu, mask) + if (xen_vcpu_stolen(cpu)) + yield = true; + + if (yield) + HYPERVISOR_sched_op(SCHEDOP_yield, 0); /* Wait for response */ while (atomic_read(&data.started) != cpus || diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index dfd6db69ead5..d083ff5ef088 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -105,6 +105,12 @@ static void get_runstate_snapshot(struct vcpu_runstate_info *res) } while (get64(&state->state_entry_time) != state_time); } +/* return true when a vcpu could run but has no real cpu to run on */ +bool xen_vcpu_stolen(int vcpu) +{ + return per_cpu(runstate, vcpu).state == RUNSTATE_runnable; +} + static void setup_runstate_info(int cpu) { struct vcpu_register_runstate_memory_area area; diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index b5697bae52d0..3847eed0bb09 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -27,6 +27,8 @@ unsigned long xen_get_wallclock(void); int xen_set_wallclock(unsigned long time); unsigned long long xen_sched_clock(void); +bool xen_vcpu_stolen(int vcpu); + void xen_mark_init_mm_pinned(void); void __init xen_fill_possible_map(void); -- cgit v1.2.2