Hello Paul E. McKenney,
The patch 7939f0d7b28c: "rcu: Restrict access to RCU CPU stall
notifiers" from Nov 1, 2023 (linux-next), leads to the following
Smatch static checker warning:
kernel/rcu/rcutorture.c:2502 rcu_torture_stall()
error: uninitialized symbol 'ret'.
kernel/rcu/rcutorture.c
2446 static int rcu_torture_stall(void *args)
2447 {
2448 int idx;
2449 int ret;
2450 unsigned long stop_at;
2451
2452 VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
2453 if (rcu_cpu_stall_notifiers) {
2454 ret = rcu_stall_chain_notifier_register(&rcu_torture_stall_block);
2455 if (ret)
2456 pr_info("%s: rcu_stall_chain_notifier_register() returned %d, %sexpected.\n",
2457 __func__, ret, !IS_ENABLED(CONFIG_RCU_STALL_COMMON) ? "un" : "");
ret is only initialized if rcu_cpu_stall_notifiers is true.
2458 }
2459 if (stall_cpu_holdoff > 0) {
2460 VERBOSE_TOROUT_STRING("rcu_torture_stall begin holdoff");
2461 schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
2462 VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
2463 }
2464 if (!kthread_should_stop() && stall_gp_kthread > 0) {
2465 VERBOSE_TOROUT_STRING("rcu_torture_stall begin GP stall");
2466 rcu_gp_set_torture_wait(stall_gp_kthread * HZ);
2467 for (idx = 0; idx < stall_gp_kthread + 2; idx++) {
2468 if (kthread_should_stop())
2469 break;
2470 schedule_timeout_uninterruptible(HZ);
2471 }
2472 }
2473 if (!kthread_should_stop() && stall_cpu > 0) {
2474 VERBOSE_TOROUT_STRING("rcu_torture_stall begin CPU stall");
2475 stop_at = ktime_get_seconds() + stall_cpu;
2476 /* RCU CPU stall is expected behavior in following code. */
2477 idx = cur_ops->readlock();
2478 if (stall_cpu_irqsoff)
2479 local_irq_disable();
2480 else if (!stall_cpu_block)
2481 preempt_disable();
2482 pr_alert("%s start on CPU %d.\n",
2483 __func__, raw_smp_processor_id());
2484 while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
2485 stop_at))
2486 if (stall_cpu_block) {
2487 #ifdef CONFIG_PREEMPTION
2488 preempt_schedule();
2489 #else
2490 schedule_timeout_uninterruptible(HZ);
2491 #endif
2492 } else if (stall_no_softlockup) {
2493 touch_softlockup_watchdog();
2494 }
2495 if (stall_cpu_irqsoff)
2496 local_irq_enable();
2497 else if (!stall_cpu_block)
2498 preempt_enable();
2499 cur_ops->readunlock(idx);
2500 }
2501 pr_alert("%s end.\n", __func__);
--> 2502 if (!ret) {
Uninitialized here
2503 if (rcu_cpu_stall_notifiers) {
But maybe we can just reverse the tests or delete one of the conditions?
2504 ret = rcu_stall_chain_notifier_unregister(&rcu_torture_stall_block);
2505 if (ret)
2506 pr_info("%s: rcu_stall_chain_notifier_unregister() returned %d.\n", __func__, ret);
2507 }
2508 }
2509 torture_shutdown_absorb("rcu_torture_stall");
2510 while (!kthread_should_stop())
2511 schedule_timeout_interruptible(10 * HZ);
2512 return 0;
2513 }
regards,
dan carpenter
