samples/bpf: xdp_redirect_cpu adjustment to reproduce teardown race easier

The teardown race in cpumap is really hard to reproduce.  These changes
makes it easier to reproduce, for QA.

The --stress-mode now have a case of a very small queue size of 8, that helps
to trigger teardown flush to encounter a full queue, which results in calling
xdp_return_frame API, in a non-NAPI protect context.

Also increase MAX_CPUS, as my QA department have larger machines than me.
Tested-by: NJean-Tsung Hsiao <jhsiao@redhat.com>
Signed-off-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

samples/bpf/xdp_redirect_cpu_kern.c

@@ -14,7 +14,7 @@
 #include <uapi/linux/bpf.h>
 #include "bpf_helpers.h"
 
-#define MAX_CPUS 12 /* WARNING - sync with _user.c */
+#define MAX_CPUS 64 /* WARNING - sync with _user.c */
 
 /* Special map type that can XDP_REDIRECT frames to another CPU */
 struct bpf_map_def SEC("maps") cpu_map = {

samples/bpf/xdp_redirect_cpu_user.c

@@ -19,7 +19,7 @@ static const char *__doc__ =
 #include <arpa/inet.h>
 #include <linux/if_link.h>
 
-#define MAX_CPUS 12 /* WARNING - sync with _kern.c */
+#define MAX_CPUS 64 /* WARNING - sync with _kern.c */
 
 /* How many xdp_progs are defined in _kern.c */
 #define MAX_PROG 5
@@ -527,7 +527,7 @@ static void stress_cpumap(void)
 	 * procedure.
 	 */
 	create_cpu_entry(1,  1024, 0, false);
-	create_cpu_entry(1,   128, 0, false);
+	create_cpu_entry(1,     8, 0, false);
 	create_cpu_entry(1, 16000, 0, false);
 }