[LTP] [PATCH v6] 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_8 -p semctl01 -i 1000

Results summary before:
Total runs:  8000
Runtime:    4m 8s
Passed:     103994
Failed:     0
Skipped:    0
Broken:     3
Warnings:   0

Results summary after:
Total runs:  8000
Runtime:    4m 8s
Passed:     104000
Failed:     0
Skipped:    0
Broken:     0
Warnings:   0

Assisted-by: Cursor

Signed-off-by: Stephen Bertram <sbertram@redhat.com>
---
 testcases/kernel/syscalls/semctl/semctl01.c | 96 ++++++++++++++-------
 1 file changed, 66 insertions(+), 30 deletions(-)

diff --git a/testcases/kernel/syscalls/semctl/semctl01.c b/testcases/kernel/syscalls/semctl/semctl01.c
index 5bd675ab6..1aa1e0a58 100644
--- a/testcases/kernel/syscalls/semctl/semctl01.c
+++ b/testcases/kernel/syscalls/semctl/semctl01.c
@@ -19,7 +19,6 @@
 #define SEMUN_CAST (union semun)
 
 static int sem_id = -1;
-static int sem_index;
 static struct semid_ds buf;
 static struct seminfo ipc_buf;
 static unsigned short array[PSEMS];
@@ -211,10 +210,8 @@ 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");
 	}
 }
@@ -236,28 +233,63 @@ 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},
 };
 
+static int try_sem_stat(union semun *arg)
+{
+	int info_id = 0;
+	int idx;
+
+	idx = SAFE_SEMCTL(info_id, 0, IPC_INFO, (union semun)&ipc_buf);
+	return semctl(idx, 0, SEM_STAT, *arg);
+}
+
+static int sem_stat_succeeded(int ret)
+{
+	if (ret >= 0)
+		return 1;
+
+	if (errno != EIDRM && errno != EINVAL)
+		tst_brk(TBROK | TERRNO, "semctl(SEM_STAT)");
+
+	return 0;
+}
+
+/*
+ * 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 ret;
+
+	ret = TST_RETRY_FUNC(try_sem_stat(&arg), sem_stat_succeeded);
+	if (ret < 0)
+		tst_brk(TBROK | TERRNO,
+			"semctl(SEM_STAT) still failing after retries");
+
+	return ret;
+}
+
 static void verify_semctl(unsigned int n)
 {
 	struct tcases *tc = &tests[n];
@@ -265,6 +297,7 @@ static void verify_semctl(unsigned int n)
 
 	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:
@@ -279,21 +312,24 @@ 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();
 }
-- 
2.55.0