This allows the user to specify a separate cpuset for the main pid,
e.g. on a housekeeping CPU.
If --mainaffinity is not specified, but --affinity is, then the
current behaviour is preserved and the main thread is bound
to the cpuset specified by --affinity

Signed-off-by: Jonathan Schwender <redacted>
---
 src/cyclictest/cyclictest.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
index 3bab3b2..a2103c7 100644
--- a/src/cyclictest/cyclictest.c
+++ b/src/cyclictest/cyclictest.c

@@ -836,6 +836,8 @@ static void display_help(int error)
 	       "	 --laptop	   Save battery when running cyclictest\n"
 	       "			   This will give you poorer realtime results\n"
 	       "			   but will not drain your battery so quickly\n"
+	       "         --mainaffinity=[CPUSET]  Run the main thread on CPU #N. This only affects\n"
+	       "                           the main thread and not the measurement threads\n"
 	       "-m       --mlockall        lock current and future memory allocations\n"
 	       "-M       --refresh_on_max  delay updating the screen until a new max\n"
 	       "			   latency is hit. Useful for low bandwidth.\n"

@@ -891,6 +893,7 @@ static int quiet;
 static int interval = DEFAULT_INTERVAL;
 static int distance = -1;
 static struct bitmask *affinity_mask = NULL;
+static struct bitmask *main_affinity_mask = NULL;
 static int smp = 0;
 static int setaffinity = AFFINITY_UNSPECIFIED;
 

@@ -944,7 +947,7 @@ enum option_values {
 	OPT_AFFINITY=1, OPT_BREAKTRACE, OPT_CLOCK,
 	OPT_DISTANCE, OPT_DURATION, OPT_LATENCY,
 	OPT_FIFO, OPT_HISTOGRAM, OPT_HISTOFALL, OPT_HISTFILE,
-	OPT_INTERVAL, OPT_LOOPS, OPT_MLOCKALL, OPT_REFRESH,
+	OPT_INTERVAL, OPT_LOOPS, OPT_MAINAFFINITY, OPT_MLOCKALL, OPT_REFRESH,
 	OPT_NANOSLEEP, OPT_NSECS, OPT_OSCOPE, OPT_PRIORITY,
 	OPT_QUIET, OPT_PRIOSPREAD, OPT_RELATIVE, OPT_RESOLUTION,
 	OPT_SYSTEM, OPT_SMP, OPT_THREADS, OPT_TRIGGER,

@@ -981,6 +984,7 @@ static void process_options(int argc, char *argv[], int max_cpus)
 			{"interval",         required_argument, NULL, OPT_INTERVAL },
 			{"laptop",	     no_argument,	NULL, OPT_LAPTOP },
 			{"loops",            required_argument, NULL, OPT_LOOPS },
+			{"mainaffinity",     required_argument, NULL, OPT_MAINAFFINITY},
 			{"mlockall",         no_argument,       NULL, OPT_MLOCKALL },
 			{"refresh_on_max",   no_argument,       NULL, OPT_REFRESH },
 			{"nsecs",            no_argument,       NULL, OPT_NSECS },

@@ -1083,6 +1087,16 @@ static void process_options(int argc, char *argv[], int max_cpus)
 		case 'l':
 		case OPT_LOOPS:
 			max_cycles = atoi(optarg); break;
+		case OPT_MAINAFFINITY:
+			if (optarg) {
+				parse_cpumask(optarg, max_cpus, &main_affinity_mask);
+			} else if (optind < argc &&
+			           (atoi(argv[optind]) ||
+			            argv[optind][0] == '0' ||
+			            argv[optind][0] == '!')) {
+				parse_cpumask(argv[optind], max_cpus, &main_affinity_mask);
+			}
+			break;
 		case 'm':
 		case OPT_MLOCKALL:
 			lockall = 1; break;

@@ -1802,7 +1816,9 @@ int main(int argc, char **argv)
 	}
 
 	/* Restrict the main pid to the affinity specified by the user */
-	if (affinity_mask != NULL) {
+	if (main_affinity_mask != NULL) {
+		set_main_thread_affinity(main_affinity_mask);