Commit c2e42230 authored Sep 30, 2016 by Syed Rameez Mustafa Committed by Satya Durga Srinivasu Prabhala Jan 02, 2019

sched: Fix CPU selection when all online CPUs are isolated

After the introduction of "33c24b sched: add cpu isolation support"
select_fallback_rq() might sometimes be unable find any CPU to place
a task on. This happens when the all online CPUs are isolated and
the allow isolated flag is set to false. In such cases, we have
little choice but to use an isolated CPU and wait for core control
to eventually un-isolate one or more online CPUs.

Change-Id: I678a0956f4fbc953b902994d687e0507ffd71f3a
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>

parent 07a16a8c

kernel/sched/core.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -1468,7 +1468,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p, bool allow_iso)
		{
		int nid = cpu_to_node(cpu);
		const struct cpumask *nodemask = NULL;
		enum { cpuset, possible, fail } state = cpuset;
		enum { cpuset, possible, fail, bug } state = cpuset;
		int dest_cpu;
		int isolated_candidate = -1;

		@@ -1524,6 +1524,11 @@ static int select_fallback_rq(int cpu, struct task_struct *p, bool allow_iso)
		break;

		case fail:
		allow_iso = true;
		state = bug;
		break;

		case bug:
		BUG();
		break;
		}