[LTP] [PATCH v8] 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 34s
Passed:     416000
Failed:     0
Skipped:    0
Broken:     0
Warnings:   0

Assisted-by: Cursor

 testcases/kernel/syscalls/semctl/semctl01.c | 40 ++++++++++++++++-----
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/testcases/kernel/syscalls/semctl/semctl01.c b/testcases/kernel/syscalls/semctl/semctl01.c
index 5bd675ab6..151061995 100644
--- a/testcases/kernel/syscalls/semctl/semctl01.c
+++ b/testcases/kernel/syscalls/semctl/semctl01.c
@@ -210,13 +210,10 @@ static void func_rmid(void)
 
 static void func_iinfo(int hidx)
 {
-	if (hidx >= 0) {
-		sem_index = hidx;
+	if (hidx >= 0)
 		tst_res(TPASS, "the highest index is correct");
-	} else {
-		sem_index = 0;
+	else
 		tst_res(TFAIL, "the highest index is incorrect");
-	}
 }
 
 static void func_sinfo(void)
@@ -229,10 +226,10 @@ static void func_sinfo(void)
 
 static void func_sstat(int semidx)
 {
-	if (semidx >= 0)
+	if (semidx == 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, semidx);
 }
 
 static struct tcases {
@@ -258,13 +255,40 @@ static struct tcases {
 	{&sem_id, 0, IPC_RMID, func_rmid, SEMUN_CAST & buf, NULL},
 };
 
+/*
+ * 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;
+	max_idx = SAFE_SEMCTL(id, 0, SEM_INFO, arg);
+
+	arg.buf = &dummy_ds;
+	for (i = 0; i <= max_idx; i++) {
+		if (semctl(i, 0, SEM_STAT, arg) == id)
+			return i;
+	}
+
+	return -1;
+}
+
 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 to idx mapping");
+	}
 	if (tc->func_setup) {
 		switch (tc->cmd) {
 		case GETNCNT:
-- 
2.55.0


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