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rcu: Add WRITE_ONCE() to rcu_node ->qsmaskinitnext
The rcu_state structure's ->qsmaskinitnext field is read locklessly, so this commit adds the WRITE_ONCE() to an update in order to provide proper documentation and READ_ONCE()/WRITE_ONCE() pairing. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely for systems not doing incessant CPU-hotplug operations. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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1 changed files with 2 additions and 2 deletions
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@ -3379,7 +3379,7 @@ void rcu_cpu_starting(unsigned int cpu)
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rnp = rdp->mynode;
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mask = rdp->grpmask;
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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rnp->qsmaskinitnext |= mask;
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WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask);
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oldmask = rnp->expmaskinitnext;
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rnp->expmaskinitnext |= mask;
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oldmask ^= rnp->expmaskinitnext;
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@ -3432,7 +3432,7 @@ void rcu_report_dead(unsigned int cpu)
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rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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}
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rnp->qsmaskinitnext &= ~mask;
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WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask);
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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raw_spin_unlock(&rcu_state.ofl_lock);
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