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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-01-04 11:33:17 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-02-20 15:58:22 -0800 |
| commit | 8ff37290d6622e130553a38ec2662a728e46cdba (patch) | |
| tree | 5e44a2a33b07485e0657433245613c0c1692fbce /kernel/rcu/tree.c | |
| parent | bfeebe24212d374f82bbf5b005371fe13acabb93 (diff) | |
| download | linux-8ff37290d6622e130553a38ec2662a728e46cdba.tar.gz | |
rcu: Add *_ONCE() for grace-period progress indicators
The various RCU structures' ->gp_seq, ->gp_seq_needed, ->gp_req_activity, and ->gp_activity fields are read locklessly, so they must be updated with WRITE_ONCE() and, when read locklessly, with READ_ONCE(). This commit makes these changes. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 346321aa3c90..53946b169699 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1175,7 +1175,7 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, TPS("Prestarted")); goto unlock_out; } - rnp->gp_seq_needed = gp_seq_req; + WRITE_ONCE(rnp->gp_seq_needed, gp_seq_req); if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) { /* * We just marked the leaf or internal node, and a @@ -1210,8 +1210,8 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, unlock_out: /* Push furthest requested GP to leaf node and rcu_data structure. */ if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) { - rnp_start->gp_seq_needed = rnp->gp_seq_needed; - rdp->gp_seq_needed = rnp->gp_seq_needed; + WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed); + WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); } if (rnp != rnp_start) raw_spin_unlock_rcu_node(rnp); @@ -1423,7 +1423,7 @@ 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) - rdp->gp_seq_needed = rnp->gp_seq_needed; + WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); return ret; @@ -3276,12 +3276,12 @@ int rcutree_prepare_cpu(unsigned int cpu) rnp = rdp->mynode; raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ rdp->beenonline = true; /* We have now been online. */ - rdp->gp_seq = rnp->gp_seq; - rdp->gp_seq_needed = rnp->gp_seq; + rdp->gp_seq = READ_ONCE(rnp->gp_seq); + rdp->gp_seq_needed = rdp->gp_seq; rdp->cpu_no_qs.b.norm = true; rdp->core_needs_qs = false; rdp->rcu_iw_pending = false; - rdp->rcu_iw_gp_seq = rnp->gp_seq - 1; + rdp->rcu_iw_gp_seq = rdp->gp_seq - 1; trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl")); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_prepare_kthreads(cpu); |