libbpf-tools/softirqslower: Fix review comments

- Use ARRAY_SIZE(stage_names) instead of magic number 2 for stage
  bounds check, so adding a new stage enum value automatically extends
  the valid range without a separate update here.
- Update man page SYNOPSIS from softirqslower.py to softirqslower to
  reflect the libbpf CO-RE binary.

Change-Id: I2c5c63282a40276a73eb37b1cae197fe83f2c374

Author: ismhong

libbpf-tools/softirqslower.c

@@ -16,6 +16,8 @@
 #include "softirqslower.skel.h"
 #include "trace_helpers.h"
 
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
+
 static volatile sig_atomic_t exiting = 0;
 
 struct env {
@@ -136,7 +138,7 @@ static void handle_event(void *ctx, int cpu, void *data, __u32 data_sz)
 
 	printf("%-8s %-20s %-8s %-14llu %-6u %-16s\n",
 			ts,
-			e.stage < 2 ? stage_names[e.stage] : "unknown",
+			e.stage < ARRAY_SIZE(stage_names) ? stage_names[e.stage] : "unknown",
 			e.vec  < NR_SOFTIRQS ? vec_names[e.vec] : "unknown",
 			e.delta_us,
 			e.cpu,

man/man8/softirqslower.8

@@ -2,10 +2,10 @@
 .SH NAME
 softirqslower \- Trace softirq handlers with latency exceeding a threshold
 .SH SYNOPSIS
-.B softirqslower.py
+.B softirqslower
 .RI [min_us]
 .br
-.B softirqslower.py
+.B softirqslower
 .RB [ \-c
 .IR CPU ]
 .RI [min_us]