diff options
| author | Zilin Guan <zilinguan811@gmail.com> | 2024-11-10 14:47:47 +0000 |
|---|---|---|
| committer | Boqun Feng <boqun.feng@gmail.com> | 2025-02-04 21:52:38 -0800 |
| commit | 764f6a81103e83dc552237f77cc769dd550d8e01 (patch) | |
| tree | 322f12267de4392f4496d86f50807cf7b1000343 | |
| parent | a3e8162105e8266b94bb25d3d7e48645da4b0c26 (diff) | |
rcu: Remove READ_ONCE() for rdp->gpwrap access in __note_gp_changes()
There is one access to the per-CPU rdp->gpwrap field in the
__note_gp_changes() function that does not use READ_ONCE(), but all other
accesses do use READ_ONCE(). When using the 8*TREE03 and CONFIG_NR_CPUS=8
configuration, KCSAN found no data races at that point. This is because
all calls to __note_gp_changes() hold rnp->lock, which excludes writes
to the rdp->gpwrap fields for all CPUs associated with that same leaf
rcu_node structure.
This commit therefore removes READ_ONCE() from rdp->gpwrap accesses
within the __note_gp_changes() function.
Signed-off-by: Zilin Guan <zilinguan811@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
| -rw-r--r-- | kernel/rcu/tree.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 475f31deed14..e4c0ce600b2b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1254,7 +1254,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) /* Handle the ends of any preceding grace periods first. */ if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) || - unlikely(READ_ONCE(rdp->gpwrap))) { + unlikely(rdp->gpwrap)) { if (!offloaded) ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */ rdp->core_needs_qs = false; @@ -1268,7 +1268,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) /* Now handle the beginnings of any new-to-this-CPU grace periods. */ if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) || - unlikely(READ_ONCE(rdp->gpwrap))) { + unlikely(rdp->gpwrap)) { /* * If the current grace period is waiting for this CPU, * set up to detect a quiescent state, otherwise don't @@ -1283,7 +1283,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); - if (IS_ENABLED(CONFIG_PROVE_RCU) && READ_ONCE(rdp->gpwrap)) + if (IS_ENABLED(CONFIG_PROVE_RCU) && rdp->gpwrap) WRITE_ONCE(rdp->last_sched_clock, jiffies); WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); |