[v2,21/59] dyndbg-test: change do_prints testpoint to accept a loopct

Commit Message

Jim Cromie March 20, 2025, 6:51 p.m. UTC

echo 1000 > /sys/module/test_dynamic_debug/parameters/do_prints

This allows its use as a scriptable load generator, to generate
dynamic-prefix-emits for flag combinations vs undecorated messages.
This will make it easy to assess the cost of the prefixing.

Reading the ./do_prints node also prints messages (once) to the-log.

NB: the count is clamped to 10000, chosen to be notice able, but not
annoying, and not enough to accidentally flood the logs.

Signed-off-by: Jim Cromie <[e-mail]>
---
 lib/test_dynamic_debug.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

Patch

diff --git a/lib/test_dynamic_debug.c b/lib/test_dynamic_debug.c
index 9f9e3fddd7e6..4a3d2612ef60 100644
--- a/lib/test_dynamic_debug.c
+++ b/lib/test_dynamic_debug.c
@@ -29,18 +29,30 @@ 
 
 #include <linux/module.h>
 
-/* re-gen output by reading or writing sysfs node: do_prints */
-
-static void do_prints(void); /* device under test */
+/* re-trigger debug output by reading or writing sysfs node: do_prints */
+#define PRINT_CLAMP 10000
+static void do_prints(unsigned int); /* device under test */
 static int param_set_do_prints(const char *instr, const struct kernel_param *kp)
 {
-	do_prints();
+	int rc;
+	unsigned int ct;
+
+	rc = kstrtouint(instr, 0, &ct);
+	if (rc) {
+		pr_err("expecting numeric input, using 1 instead\n");
+		ct = 1;
+	}
+	if (ct > PRINT_CLAMP) {
+		ct = PRINT_CLAMP;
+		pr_info("clamping print-count to %d\n", ct);
+	}
+	do_prints(ct);
 	return 0;
 }
 static int param_get_do_prints(char *buffer, const struct kernel_param *kp)
 {
-	do_prints();
-	return scnprintf(buffer, PAGE_SIZE, "did do_prints\n");
+	do_prints(1);
+	return scnprintf(buffer, PAGE_SIZE, "did 1 do_prints\n");
 }
 static const struct kernel_param_ops param_ops_do_prints = {
 	.set = param_set_do_prints,
@@ -191,17 +203,20 @@  static void do_levels(void)
 	prdbg(V7);
 }
 
-static void do_prints(void)
+static void do_prints(unsigned int ct)
 {
-	pr_debug("do_prints:\n");
-	do_cats();
-	do_levels();
+	/* maybe clamp this */
+	pr_debug("do-prints %d times:\n", ct);
+	for (; ct; ct--) {
+		do_cats();
+		do_levels();
+	}
 }
 
 static int __init test_dynamic_debug_init(void)
 {
 	pr_debug("init start\n");
-	do_prints();
+	do_prints(1);
 	pr_debug("init done\n");
 	return 0;
 }