[LTP] [PATCH v11] semctl01: fix SEM_STAT failures under parallel LTP runs

[Stephen Bertram via ltp <ltp@lists.linux.it>]

SEM_STAT was using the global high index from IPC_INFO, which is not
stable when other IPC tests run in parallel and can abort the test with
TBROK.

Signed-off-by: Stephen Bertram <sbertram@redhat.com>
---
Test: ./kirk -w 4 -f syscalls_32 -p semctl01 -i 1000

Before changes:
Total runs:  32000
Runtime:    16m 32s
Passed:     415968
Failed:     0
Skipped:    0
Broken:     16
Warnings:   0

After changes:
Total runs:  32000
Runtime:    16m 35s
Passed:     416000
Failed:     0
Skipped:    0
Broken:     0
Warnings:   0

Assisted-by: Cursor

 testcases/kernel/syscalls/semctl/semctl01.c | 59 +++++++++++++++++----
 1 file changed, 48 insertions(+), 11 deletions(-)

diff --git a/testcases/kernel/syscalls/semctl/semctl01.c b/testcases/kernel/syscalls/semctl/semctl01.c
index 5bd675ab6..1627a07a7 100644
--- a/testcases/kernel/syscalls/semctl/semctl01.c
+++ b/testcases/kernel/syscalls/semctl/semctl01.c
@@ -210,13 +210,16 @@ static void func_rmid(void)
 
 static void func_iinfo(int hidx)
 {
-	if (hidx >= 0) {
-		sem_index = hidx;
-		tst_res(TPASS, "the highest index is correct");
-	} else {
-		sem_index = 0;
-		tst_res(TFAIL, "the highest index is incorrect");
-	}
+	/*
+	 * Return value is the highest used index. Our set is alive, so the
+	 * highest used index must be at least our index.
+	 */
+	if (hidx >= sem_index)
+		tst_res(TPASS, "IPC_INFO highest index %d >= our index %d",
+			hidx, sem_index);
+	else
+		tst_res(TFAIL, "IPC_INFO highest index %d < our index %d",
+			hidx, sem_index);
 }
 
 static void func_sinfo(void)
@@ -227,12 +230,40 @@ static void func_sinfo(void)
 		tst_res(TPASS, "number of semaphore sets is correct");
 }
 
-static void func_sstat(int semidx)
+static void func_sstat(int semid)
 {
-	if (semidx >= 0)
+	if (semid == sem_id)
 		tst_res(TPASS, "id of the semaphore set is correct");
 	else
-		tst_res(TFAIL, "id of the semaphore set is incorrect");
+		tst_res(TFAIL, "expected sem_id %d, got %d", sem_id, semid);
+}
+
+/*
+ * SEM_STAT takes an index into the kernel's internal array, not a semid.
+ * Return the index that maps to this test's set.
+ */
+static int get_sem_idx_from_id(int id)
+{
+	struct seminfo info;
+	struct semid_ds dummy_ds;
+	union semun arg;
+	int max_idx, i;
+
+	arg.__buf = &info;
+	/* SEM_INFO ignores semid; but SAFE_SEMCTL requires an lvalue */
+	max_idx = SAFE_SEMCTL(id, 0, SEM_INFO, arg);
+
+	arg.buf = &dummy_ds;
+	for (i = 0; i <= max_idx; i++) {
+		/*
+		 * Bare semctl: unused/unreadable indices fail with
+		 * EINVAL/EACCES; SAFE_SEMCTL would abort the test.
+		 */
+		if (semctl(i, 0, SEM_STAT, arg) == id)
+			return i;
+	}
+
+	return -1;
 }
 
 static struct tcases {
@@ -263,8 +294,14 @@ static void verify_semctl(unsigned int n)
 	struct tcases *tc = &tests[n];
 	int rval;
 
-	if (sem_id == -1)
+	if (sem_id == -1) {
 		sem_id = SAFE_SEMGET(IPC_PRIVATE, PSEMS, IPC_CREAT | IPC_EXCL | SEM_RA);
+		sem_index = get_sem_idx_from_id(sem_id);
+		if (sem_index < 0)
+			tst_brk(TBROK,
+				"Failed to get sem_id %d to idx mapping", sem_id);
+		tst_res(TINFO, "sem_id=%d maps to kernel index=%d", sem_id, sem_index);
+	}
 	if (tc->func_setup) {
 		switch (tc->cmd) {
 		case GETNCNT:
-- 
2.55.0


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