Function tryResetCPUAffinity

libcontainer/process_linux.go:185–212

tryResetCPUAffinity tries to reset the CPU affinity of the process identified by pid to include all possible CPUs (notwithstanding cgroup cpuset restrictions, isolated CPUs and CPU online status).

(pid int)

// identified by pid to include all possible CPUs (notwithstanding cgroup
// cpuset restrictions, isolated CPUs and CPU online status).
func tryResetCPUAffinity(pid int) {
	// When resetting the CPU affinity, we want to allow all
	// possible CPUs in the system, including those not in
	// cpuset.cpus, online or even present (hot-plugged) at call
	// time. Using a cpumask any tighter this that may disallow
	// using those CPUs if they are added to cpuset.cpus later.
	//
	// Note that sched_setaffinity(2) will implicitly:
	//
	//  * Clamp the cpumask so that it matches the number of CPUs
	//    supported by the kernel.
	//
	//  * Mask out any CPUs that are not a member of the target task's
	//    configured cgroup cpuset. This is for task's effective affinity,
	//    without forgetting masked-out CPUs should the cgroup cpuset
	//    change later.
	//
	// Therefore, preparing the cpumask, we can avoid reading
	// /sys/devices/system/cpu/possible and kernel_max.
	// Instead, we use a huge buffer similarly to go 1.25 runtime in
	// getCPUCount().
	const maxCPUs = 64 * 1024
	buf := bytes.Repeat([]byte{0xff}, maxCPUs/8)
	if err := linux.SchedSetaffinity(pid, buf); err != nil {
		logrus.WithError(err).Warnf("resetting the CPU affinity of pid %d failed -- the container process may inherit runc's CPU affinity", pid)
		return
	}
}

// Starts setns process with specified initial CPU affinity.
func (p *setnsProcess) startWithCPUAffinity() error {