[LTP] [PATCH v2] mem/min_free_kbytes: Fix incorrect pass/fail accounting

[Sachin Sant]

When check_monitor() detected a violation (MemFree < min_free_kbytes) it
called tst_res(TFAIL, ...) from the child process, which atomically
incremented the shared results->failed counter, and then the child exited
with status 0. Back in the parent, min_free_kbytes_test() checked the
child exit status, found it was 0, and fell through to the unconditional
tst_res(TPASS, ...) at the end of the function.

This produced a misleading summary of 'passed 1 / failed 1' on violation:
the TFAIL from the monitor child was correctly counted, but the
unconditional TPASS that followed also added to the pass count regardless
of the violation.

Fix this by moving TPASS/TFAIL reporting into check_monitor() in the child
process. Emit tst_res(TFAIL, ...) immediately on each individual violation
so that the TINFO diagnostic and its corresponding TFAIL are always paired;
the 'violated' flag is kept to suppress the final TPASS when any breach was
seen. Emit tst_res(TPASS, ...) only when no violation was observed across
the entire monitoring run.
The parent's wait-result block is changed to guard against unexpected
termination (signal death or non-zero exit) only; it emits no result for
the monitor outcome since that is already reported by the child. The
original condition WIFEXITED && WEXITSTATUS != 0 missed signal death;
the corrected condition is !WIFEXITED || WEXITSTATUS != 0.

After the fix the summary correctly reflects the outcome:
- No violation:  passed 1 / failed 0
- Violation:     passed 0 / failed N  (one TFAIL per breached sample)

Signed-off-by: Sachin Sant <sachinp@linux.ibm.com>
---
v1 -> v2:
- Addressed review comments by moving TPASS/TFAIL reporting
  into check_monitor() in the child process.

---
 testcases/kernel/mem/tunable/min_free_kbytes.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/testcases/kernel/mem/tunable/min_free_kbytes.c b/testcases/kernel/mem/tunable/min_free_kbytes.c
index bdc9126c2..132c8fe70 100644
--- a/testcases/kernel/mem/tunable/min_free_kbytes.c
+++ b/testcases/kernel/mem/tunable/min_free_kbytes.c
@@ -68,11 +68,9 @@ static void min_free_kbytes_test(void)
 	SAFE_KILL(pid, SIGUSR1);
 	SAFE_WAITPID(pid, &status, WUNTRACED | WCONTINUED);
 
-	if (WIFEXITED(status) && WEXITSTATUS(status) != 0)
-		tst_res(TFAIL, "check_monitor child exit with status: %s",
+	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
+		tst_res(TFAIL, "check_monitor child failed: %s",
 			tst_strstatus(status));
-
-	tst_res(TPASS, "min_free_kbytes test pass");
 }
 
 static void test_tune(unsigned long overcommit_policy)
@@ -173,6 +171,7 @@ static int eatup_mem(unsigned long overcommit_policy)
 
 static void check_monitor(void)
 {
+	int violated = 0;
 	unsigned long tune;
 	unsigned long memfree;
 
@@ -182,12 +181,16 @@ static void check_monitor(void)
 
 		if (memfree < tune) {
 			tst_res(TINFO, "MemFree is %lu kB, "
-				 "min_free_kbytes is %lu kB", memfree, tune);
+				"min_free_kbytes is %lu kB", memfree, tune);
 			tst_res(TFAIL, "MemFree < min_free_kbytes");
+			violated = 1;
 		}
 
 		sleep(2);
 	}
+
+	if (!violated)
+		tst_res(TPASS, "min_free_kbytes test pass");
 }
 
 static void sighandler(int signo LTP_ATTRIBUTE_UNUSED)
-- 
2.39.1