Le 02/04/2025 à 19:41, Jim Cromie a écrit :
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 <jim.cro...@gmail.com>
Reviewed-by: Louis Chauvet <louis.chau...@bootlin.com>
I think this could be in a separate series / merged independently to
reduce the size of this series.
---
lib/test_dynamic_debug.c | 37 ++++++++++++++++++++++++++-----------
1 file changed, 26 insertions(+), 11 deletions(-)
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;
}
--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
