kernel/rcu/srcutree.c:1644 srcu_advance_state() warn: inconsistent returns '&ssp->srcu_sup->srcu_gp_mutex'.
From: Dan Carpenter
Date: Sat May 06 2023 - 03:22:18 EST
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 418d5c98319f67b9ae651babea031b5394425c18
commit: e3a6ab25cfa0fcdcb31c346b9871a566d440980d srcu: Move ->srcu_gp_mutex from srcu_struct to srcu_usage
config: x86_64-randconfig-m001-20230501 (https://download.01.org/0day-ci/archive/20230506/202305060951.I8mz6eHt-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <error27@xxxxxxxxx>
| Link: https://lore.kernel.org/r/202305060951.I8mz6eHt-lkp@xxxxxxxxx/
smatch warnings:
kernel/rcu/srcutree.c:1644 srcu_advance_state() warn: inconsistent returns '&ssp->srcu_sup->srcu_gp_mutex'.
vim +1644 kernel/rcu/srcutree.c
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1584 static void srcu_advance_state(struct srcu_struct *ssp)
dad81a2026841b Paul E. McKenney 2017-03-25 1585 {
dad81a2026841b Paul E. McKenney 2017-03-25 1586 int idx;
dad81a2026841b Paul E. McKenney 2017-03-25 1587
e3a6ab25cfa0fc Paul E. McKenney 2023-03-17 1588 mutex_lock(&ssp->srcu_sup->srcu_gp_mutex);
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1589
dad81a2026841b Paul E. McKenney 2017-03-25 1590 /*
dad81a2026841b Paul E. McKenney 2017-03-25 1591 * Because readers might be delayed for an extended period after
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1592 * fetching ->srcu_idx for their index, at any point in time there
dad81a2026841b Paul E. McKenney 2017-03-25 1593 * might well be readers using both idx=0 and idx=1. We therefore
dad81a2026841b Paul E. McKenney 2017-03-25 1594 * need to wait for readers to clear from both index values before
dad81a2026841b Paul E. McKenney 2017-03-25 1595 * invoking a callback.
dad81a2026841b Paul E. McKenney 2017-03-25 1596 *
dad81a2026841b Paul E. McKenney 2017-03-25 1597 * The load-acquire ensures that we see the accesses performed
dad81a2026841b Paul E. McKenney 2017-03-25 1598 * by the prior grace period.
dad81a2026841b Paul E. McKenney 2017-03-25 1599 */
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1600 idx = rcu_seq_state(smp_load_acquire(&ssp->srcu_gp_seq)); /* ^^^ */
dad81a2026841b Paul E. McKenney 2017-03-25 1601 if (idx == SRCU_STATE_IDLE) {
b3fb11f7e9c3c6 Paul E. McKenney 2023-03-17 1602 spin_lock_irq_rcu_node(ssp->srcu_sup);
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1603 if (ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)) {
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1604 WARN_ON_ONCE(rcu_seq_state(ssp->srcu_gp_seq));
b3fb11f7e9c3c6 Paul E. McKenney 2023-03-17 1605 spin_unlock_irq_rcu_node(ssp->srcu_sup);
e3a6ab25cfa0fc Paul E. McKenney 2023-03-17 1606 mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
dad81a2026841b Paul E. McKenney 2017-03-25 1607 return;
dad81a2026841b Paul E. McKenney 2017-03-25 1608 }
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1609 idx = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq));
dad81a2026841b Paul E. McKenney 2017-03-25 1610 if (idx == SRCU_STATE_IDLE)
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1611 srcu_gp_start(ssp);
b3fb11f7e9c3c6 Paul E. McKenney 2023-03-17 1612 spin_unlock_irq_rcu_node(ssp->srcu_sup);
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1613 if (idx != SRCU_STATE_IDLE) {
e3a6ab25cfa0fc Paul E. McKenney 2023-03-17 1614 mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
dad81a2026841b Paul E. McKenney 2017-03-25 1615 return; /* Someone else started the grace period. */
dad81a2026841b Paul E. McKenney 2017-03-25 1616 }
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1617 }
dad81a2026841b Paul E. McKenney 2017-03-25 1618
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1619 if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN1) {
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1620 idx = 1 ^ (ssp->srcu_idx & 1);
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1621 if (!try_check_zero(ssp, idx, 1)) {
e3a6ab25cfa0fc Paul E. McKenney 2023-03-17 1622 mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
dad81a2026841b Paul E. McKenney 2017-03-25 1623 return; /* readers present, retry later. */
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1624 }
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1625 srcu_flip(ssp);
b3fb11f7e9c3c6 Paul E. McKenney 2023-03-17 1626 spin_lock_irq_rcu_node(ssp->srcu_sup);
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1627 rcu_seq_set_state(&ssp->srcu_gp_seq, SRCU_STATE_SCAN2);
282d8998e9979c Paul E. McKenney 2022-03-08 1628 ssp->srcu_n_exp_nodelay = 0;
b3fb11f7e9c3c6 Paul E. McKenney 2023-03-17 1629 spin_unlock_irq_rcu_node(ssp->srcu_sup);
dad81a2026841b Paul E. McKenney 2017-03-25 1630 }
dad81a2026841b Paul E. McKenney 2017-03-25 1631
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1632 if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN2) {
We don't mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex) if this if
statement is false.
dad81a2026841b Paul E. McKenney 2017-03-25 1633
dad81a2026841b Paul E. McKenney 2017-03-25 1634 /*
dad81a2026841b Paul E. McKenney 2017-03-25 1635 * SRCU read-side critical sections are normally short,
dad81a2026841b Paul E. McKenney 2017-03-25 1636 * so check at least twice in quick succession after a flip.
dad81a2026841b Paul E. McKenney 2017-03-25 1637 */
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1638 idx = 1 ^ (ssp->srcu_idx & 1);
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 1639 if (!try_check_zero(ssp, idx, 2)) {
e3a6ab25cfa0fc Paul E. McKenney 2023-03-17 1640 mutex_unlock(&ssp->srcu_sup->srcu_gp_mutex);
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1641 return; /* readers present, retry later. */
da915ad5cf25b5 Paul E. McKenney 2017-04-05 1642 }
282d8998e9979c Paul E. McKenney 2022-03-08 1643 ssp->srcu_n_exp_nodelay = 0;
aacb5d91ab1bfb Paul E. McKenney 2018-10-28 @1644 srcu_gp_end(ssp); /* Releases ->srcu_gp_mutex. */
dad81a2026841b Paul E. McKenney 2017-03-25 1645 }
dad81a2026841b Paul E. McKenney 2017-03-25 1646 }
--
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