sched: fix a bug in sched domain degenerate (f29c9b1c) · Commits · e / devices / android_kernel_fairphone_FP5

Impact: re-add incorrectly eliminated sched domain layers (1) on i386 with SCHED_SMT and SCHED_MC enabled # mount -t cgroup -o cpuset xxx /mnt # echo 0 > /mnt/cpuset.sched_load_balance # mkdir /mnt/0 # echo 0 > /mnt/0/cpuset.cpus # dmesg CPU0 attaching sched-domain: domain 0: span 0 level CPU groups: 0 (2) on i386 with SCHED_MC enabled but SCHED_SMT disabled # same with (1) # dmesg CPU0 attaching NULL sched-domain. The bug is that some sched domains may be skipped unintentionally when degenerating (optimizing) sched domains. Signed-off-by:

Li Zefan <lizf@cn.fujitsu.com> Acked-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+4 −2

Original line number	Original line	Diff line number	Diff line
	@@ -6877,15 +6877,17 @@ cpu_attach_domain(struct sched_domain sd, struct root_domain rd, int cpu)
	struct sched_domain *tmp;		struct sched_domain *tmp;

	/* Remove the sched domains which do not contribute to scheduling. */		/* Remove the sched domains which do not contribute to scheduling. */
	for (tmp = sd; tmp; tmp = tmp->parent) {		for (tmp = sd; tmp; ) {
	struct sched_domain *parent = tmp->parent;		struct sched_domain *parent = tmp->parent;
	if (!parent)		if (!parent)
	break;		break;

	if (sd_parent_degenerate(tmp, parent)) {		if (sd_parent_degenerate(tmp, parent)) {
	tmp->parent = parent->parent;		tmp->parent = parent->parent;
	if (parent->parent)		if (parent->parent)
	parent->parent->child = tmp;		parent->parent->child = tmp;
	}		} else
			tmp = tmp->parent;
	}		}

	if (sd && sd_degenerate(sd)) {		if (sd && sd_degenerate(sd)) {