Merge pull request #45357 from tklauser/sched-getaffinity-pid-zero

pkg/sysinfo: omit Getpid call in numCPU

pkg/sysinfo/numcpu_linux.go

@@ -1,23 +1,17 @@
 package sysinfo // import "github.com/docker/docker/pkg/sysinfo"
 
-import (
-	"golang.org/x/sys/unix"
-)
+import "golang.org/x/sys/unix"
 
 // numCPU queries the system for the count of threads available
 // for use to this process.
 //
-// Issues two syscalls.
 // Returns 0 on errors. Use |runtime.NumCPU| in that case.
 func numCPU() int {
 	// Gets the affinity mask for a process: The very one invoking this function.
-	pid := unix.Getpid()
-
 	var mask unix.CPUSet
-	err := unix.SchedGetaffinity(pid, &mask)
+	err := unix.SchedGetaffinity(0, &mask)
 	if err != nil {
 		return 0
 	}
-
 	return mask.Count()
 }