[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen: sched: don't call hooks of the wrong scheduler via VCPU2OP
Within context_saved(), we call the context_saved hook, and we use VCPU2OP() to determine from what scheduler. VCPU2OP uses DOM2OP, which uses d->cpupool, which is NULL when d is the idle domain. And in that case, DOM2OP just returns ops, the scheduler of cpupool0. Therefore, if: - cpupool0's scheduler defines context_saved (like Credit2 and RTDS do), - we are not in cpupool0 (i.e., our scheduler is not ops), - we are context switching from idle, we call VCPU2OP(idle_vcpu), which means DOM2OP(idle->cpupool), which is ops. Therefore, we both: - check if context_saved is defined in the wrong scheduler; - if yes, call the wrong one. When using Credit2 at boot, and also Credit2 in the other cpupool, this is wrong but innocuous, because it only involves the idle vcpus. When using Credit2 at boot, and Credit1 in the other cpupool, this is *totally* wrong, and it's by chance it does not explode! When using Credit2 and other schedulers I'm developping, I hit the following assert (in sched_credit2.c, on a CPU inside a cpupool that does not use Credit2): csched2_context_saved() { ... ASSERT(!vcpu_on_runq(svc)); ... } Fix this by taking care, in VCPU2OP, of the case when the vcpu is an idle one. Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx> --- Cc: George Dunlap <george.dunlap@xxxxxxxxxx> Cc: Juergen Gross <jgross@xxxxxxxx> Cc: Jan Beulich <jbeulich@xxxxxxxx> --- Cc-ing Jan, as this should be backported at least to 4.8, but, IMO, as back as possible. --- xen/common/schedule.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/xen/common/schedule.c b/xen/common/schedule.c index 223a120..d12f346 100644 --- a/xen/common/schedule.c +++ b/xen/common/schedule.c @@ -78,7 +78,19 @@ static struct scheduler __read_mostly ops; : (typeof((opsptr)->fn(opsptr, ##__VA_ARGS__)))0 ) #define DOM2OP(_d) (((_d)->cpupool == NULL) ? &ops : ((_d)->cpupool->sched)) -#define VCPU2OP(_v) (DOM2OP((_v)->domain)) +static inline struct scheduler* VCPU2OP(const struct vcpu *v) +{ + struct domain *d = v->domain; + + if ( likely(d->cpupool != NULL) ) + return d->cpupool->sched; + + /* v->processor never changes for idle vcpus, so using it here is safe */ + if ( likely(is_idle_domain(d)) ) + return per_cpu(scheduler, v->processor); + else + return &ops; +} #define VCPU2ONLINE(_v) cpupool_domain_cpumask((_v)->domain) static inline void trace_runstate_change(struct vcpu *v, int new_state) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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