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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>
This commit is contained in:
parent
bfeebe2421
commit
8ff37290d6
3 changed files with 23 additions and 19 deletions
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@ -1175,7 +1175,7 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
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TPS("Prestarted"));
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goto unlock_out;
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}
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rnp->gp_seq_needed = gp_seq_req;
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WRITE_ONCE(rnp->gp_seq_needed, gp_seq_req);
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if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) {
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/*
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* We just marked the leaf or internal node, and a
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@ -1210,8 +1210,8 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
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unlock_out:
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/* Push furthest requested GP to leaf node and rcu_data structure. */
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if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) {
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rnp_start->gp_seq_needed = rnp->gp_seq_needed;
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rdp->gp_seq_needed = rnp->gp_seq_needed;
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WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed);
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WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
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}
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if (rnp != rnp_start)
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raw_spin_unlock_rcu_node(rnp);
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@ -1423,7 +1423,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
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}
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rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */
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if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap)
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rdp->gp_seq_needed = rnp->gp_seq_needed;
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WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
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WRITE_ONCE(rdp->gpwrap, false);
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rcu_gpnum_ovf(rnp, rdp);
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return ret;
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@ -3276,12 +3276,12 @@ int rcutree_prepare_cpu(unsigned int cpu)
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rnp = rdp->mynode;
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raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
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rdp->beenonline = true; /* We have now been online. */
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rdp->gp_seq = rnp->gp_seq;
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rdp->gp_seq_needed = rnp->gp_seq;
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rdp->gp_seq = READ_ONCE(rnp->gp_seq);
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rdp->gp_seq_needed = rdp->gp_seq;
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rdp->cpu_no_qs.b.norm = true;
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rdp->core_needs_qs = false;
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rdp->rcu_iw_pending = false;
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rdp->rcu_iw_gp_seq = rnp->gp_seq - 1;
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rdp->rcu_iw_gp_seq = rdp->gp_seq - 1;
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trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl"));
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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rcu_prepare_kthreads(cpu);
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@ -753,7 +753,7 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
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raw_lockdep_assert_held_rcu_node(rnp);
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pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
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__func__, rnp->grplo, rnp->grphi, rnp->level,
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(long)rnp->gp_seq, (long)rnp->completedqs);
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(long)READ_ONCE(rnp->gp_seq), (long)rnp->completedqs);
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for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)
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pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx\n",
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__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext);
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@ -592,21 +592,22 @@ void show_rcu_gp_kthreads(void)
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(long)READ_ONCE(rcu_get_root()->gp_seq_needed),
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READ_ONCE(rcu_state.gp_flags));
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rcu_for_each_node_breadth_first(rnp) {
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if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed))
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if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),
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READ_ONCE(rnp->gp_seq_needed)))
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continue;
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pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",
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rnp->grplo, rnp->grphi, (long)rnp->gp_seq,
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(long)rnp->gp_seq_needed);
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rnp->grplo, rnp->grphi, (long)READ_ONCE(rnp->gp_seq),
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(long)READ_ONCE(rnp->gp_seq_needed));
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if (!rcu_is_leaf_node(rnp))
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continue;
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for_each_leaf_node_possible_cpu(rnp, cpu) {
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rdp = per_cpu_ptr(&rcu_data, cpu);
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if (rdp->gpwrap ||
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ULONG_CMP_GE(rcu_state.gp_seq,
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rdp->gp_seq_needed))
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ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),
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READ_ONCE(rdp->gp_seq_needed)))
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continue;
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pr_info("\tcpu %d ->gp_seq_needed %ld\n",
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cpu, (long)rdp->gp_seq_needed);
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cpu, (long)READ_ONCE(rdp->gp_seq_needed));
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}
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}
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for_each_possible_cpu(cpu) {
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@ -631,7 +632,8 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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static atomic_t warned = ATOMIC_INIT(0);
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if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed))
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ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq),
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READ_ONCE(rnp_root->gp_seq_needed)))
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return;
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j = jiffies; /* Expensive access, and in common case don't get here. */
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if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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@ -642,7 +644,8 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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j = jiffies;
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if (rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
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ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq),
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READ_ONCE(rnp_root->gp_seq_needed)) ||
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time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
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atomic_read(&warned)) {
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@ -655,9 +658,10 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */
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j = jiffies;
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if (rcu_gp_in_progress() ||
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ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
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time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
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time_before(j, rcu_state.gp_activity + gpssdelay) ||
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ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq),
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READ_ONCE(rnp_root->gp_seq_needed)) ||
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time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
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time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
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atomic_xchg(&warned, 1)) {
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if (rnp_root != rnp)
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/* irqs remain disabled. */
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