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rcu: Add READ_ONCE() to rcu_node ->gp_seq
The rcu_node structure's ->gp_seq field is read locklessly, so this commit adds the READ_ONCE() to several loads in order to avoid destructive compiler optimizations. This data race was reported by KCSAN. Not appropriate for backporting because this affects only tracing and warnings. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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b0c18c8773
commit
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1 changed files with 5 additions and 4 deletions
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@ -1126,8 +1126,9 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
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static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
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unsigned long gp_seq_req, const char *s)
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{
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trace_rcu_future_grace_period(rcu_state.name, rnp->gp_seq, gp_seq_req,
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rnp->level, rnp->grplo, rnp->grphi, s);
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trace_rcu_future_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
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gp_seq_req, rnp->level,
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rnp->grplo, rnp->grphi, s);
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}
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/*
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@ -1904,7 +1905,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
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rnp_c = rnp;
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rnp = rnp->parent;
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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oldmask = rnp_c->qsmask;
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oldmask = READ_ONCE(rnp_c->qsmask);
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}
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/*
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@ -2052,7 +2053,7 @@ int rcutree_dying_cpu(unsigned int cpu)
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return 0;
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blkd = !!(rnp->qsmask & rdp->grpmask);
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trace_rcu_grace_period(rcu_state.name, rnp->gp_seq,
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trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
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blkd ? TPS("cpuofl") : TPS("cpuofl-bgp"));
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return 0;
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}
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