[LTP] [PATCH v3] semctl01: tolerate SEM_STAT races under parallel LTP runs

[Stephen Bertram]

When multiple LTP workers run IPC tests concurrently, SEM_STAT can fail
with EIDRM/EINVAL because the index from IPC_INFO can disappear before
SEM_STAT runs. Retry a few times instead of treating that as TBROK.

The test remains single-threaded; shared globals are intentional.

Test: ./kirk -w 4 -f syscalls_32 -p semctl01 -i 1000

Results summary before:
runtime:      997.690s
passed        415980
failed        0
broken        10
skipped       0
warnings      0

Results summary after:
runtime:      998.593s
passed        416000
failed        0
broken        0
skipped       0
warnings      0

Assisted-by: Cursor

Signed-off-by: Stephen Bertram <sbertram@redhat.com>
---
 testcases/kernel/syscalls/semctl/semctl01.c | 90 ++++++++++++++-------
 1 file changed, 61 insertions(+), 29 deletions(-)

diff --git a/testcases/kernel/syscalls/semctl/semctl01.c b/testcases/kernel/syscalls/semctl/semctl01.c
index 5bd675ab6..e5056e8e3 100644
--- a/testcases/kernel/syscalls/semctl/semctl01.c
+++ b/testcases/kernel/syscalls/semctl/semctl01.c
@@ -236,35 +236,58 @@ static void func_sstat(int semidx)
 }
 
 static struct tcases {
-	int *semid;
 	int semnum;
 	int cmd;
 	void (*func_test) ();
 	union semun arg;
 	void (*func_setup) ();
 } tests[] = {
-	{&sem_id, 0, IPC_STAT, func_stat, SEMUN_CAST & buf, NULL},
-	{&sem_id, 0, IPC_SET, func_set, SEMUN_CAST & buf, set_setup},
-	{&sem_id, 0, GETALL, func_gall, SEMUN_CAST array, NULL},
-	{&sem_id, 4, GETNCNT, func_cnt, SEMUN_CAST & buf, cnt_setup},
-	{&sem_id, 2, GETPID, func_pid, SEMUN_CAST & buf, pid_setup},
-	{&sem_id, 2, GETVAL, func_gval, SEMUN_CAST & buf, NULL},
-	{&sem_id, 4, GETZCNT, func_cnt, SEMUN_CAST & buf, cnt_setup},
-	{&sem_id, 0, SETALL, func_sall, SEMUN_CAST array, sall_setup},
-	{&sem_id, 4, SETVAL, func_sval, SEMUN_CAST INCVAL, NULL},
-	{&sem_id, 0, IPC_INFO, func_iinfo, SEMUN_CAST & ipc_buf, NULL},
-	{&sem_id, 0, SEM_INFO, func_sinfo, SEMUN_CAST & ipc_buf, NULL},
-	{&sem_index, 0, SEM_STAT, func_sstat, SEMUN_CAST & buf, NULL},
-	{&sem_id, 0, IPC_RMID, func_rmid, SEMUN_CAST & buf, NULL},
+	{0, IPC_STAT, func_stat, SEMUN_CAST & buf, NULL},
+	{0, IPC_SET, func_set, SEMUN_CAST & buf, set_setup},
+	{0, GETALL, func_gall, SEMUN_CAST array, NULL},
+	{4, GETNCNT, func_cnt, SEMUN_CAST & buf, cnt_setup},
+	{2, GETPID, func_pid, SEMUN_CAST & buf, pid_setup},
+	{2, GETVAL, func_gval, SEMUN_CAST & buf, NULL},
+	{4, GETZCNT, func_cnt, SEMUN_CAST & buf, cnt_setup},
+	{0, SETALL, func_sall, SEMUN_CAST array, sall_setup},
+	{4, SETVAL, func_sval, SEMUN_CAST INCVAL, NULL},
+	{0, IPC_INFO, func_iinfo, SEMUN_CAST & ipc_buf, NULL},
+	{0, SEM_INFO, func_sinfo, SEMUN_CAST & ipc_buf, NULL},
+	{0, SEM_STAT, func_sstat, SEMUN_CAST & buf, NULL},
+	{0, IPC_RMID, func_rmid, SEMUN_CAST & buf, NULL},
 };
 
+/*
+ * SEM_STAT takes an ipc idr index. Under parallel IPC tests that index can
+ * vanish between IPC_INFO and SEM_STAT (EIDRM/EINVAL). Refresh and retry.
+ */
+static int do_sem_stat(union semun arg)
+{
+	int idx, rval;
+	unsigned int retries = 5;
+
+	do {
+		idx = semctl(0, 0, IPC_INFO, (union semun)&ipc_buf);
+		if (idx < 0)
+			tst_brk(TBROK | TERRNO, "semctl(0, 0, IPC_INFO)");
+		rval = semctl(idx, 0, SEM_STAT, arg);
+		if (rval >= 0) {
+			sem_index = idx;
+			return rval;
+		}
+		if (errno != EIDRM && errno != EINVAL)
+			tst_brk(TBROK | TERRNO, "semctl(SEM_STAT)");
+	} while (--retries);
+
+	tst_brk(TBROK | TERRNO, "semctl(SEM_STAT) still failing after retries");
+	return -1;
+}
+
 static void verify_semctl(unsigned int n)
 {
 	struct tcases *tc = &tests[n];
 	int rval;
 
-	if (sem_id == -1)
-		sem_id = SAFE_SEMGET(IPC_PRIVATE, PSEMS, IPC_CREAT | IPC_EXCL | SEM_RA);
 	if (tc->func_setup) {
 		switch (tc->cmd) {
 		case GETNCNT:
@@ -279,25 +302,33 @@ static void verify_semctl(unsigned int n)
 		}
 	}
 
-	rval = SAFE_SEMCTL(*(tc->semid), tc->semnum, tc->cmd, tc->arg);
-	switch (tc->cmd) {
-	case GETNCNT:
-	case GETZCNT:
-	case GETPID:
-	case GETVAL:
-	case IPC_INFO:
-	case SEM_STAT:
+	if (tc->cmd == SEM_STAT) {
+		rval = do_sem_stat(tc->arg);
 		tc->func_test(rval);
-		break;
-	default:
-		tc->func_test();
-		break;
+	} else {
+		rval = SAFE_SEMCTL(sem_id, tc->semnum, tc->cmd, tc->arg);
+		switch (tc->cmd) {
+		case GETNCNT:
+		case GETZCNT:
+		case GETPID:
+		case GETVAL:
+		case IPC_INFO:
+			tc->func_test(rval);
+			break;
+		default:
+			tc->func_test();
+			break;
+		}
 	}
-
 	if (tc->cmd == GETNCNT || tc->cmd == GETZCNT)
 		kill_all_children();
 }
 
+static void setup(void)
+{
+	sem_id = SAFE_SEMGET(IPC_PRIVATE, PSEMS, IPC_CREAT | IPC_EXCL | SEM_RA);
+}
+
 static void cleanup(void)
 {
 	if (sem_id >= 0)
@@ -305,6 +336,7 @@ static void cleanup(void)
 }
 
 static struct tst_test test = {
+	.setup = setup,
 	.cleanup = cleanup,
 	.test = verify_semctl,
 	.tcnt = ARRAY_SIZE(tests),
-- 
2.55.0