srcu: Fix __call_srcu()/process_srcu() datarace (7ff8b450) · Commits · 戴 / test

The srcu_node structure's ->srcu_gp_seq_needed_exp field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_ONCE() invocations. 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>

kernel/rcu/srcutree.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -550,7 +550,7 @@ static void srcu_gp_end(struct srcu_struct *ssp)
		snp->srcu_have_cbs[idx] = gpseq;
		rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1);
		if (ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, gpseq))
		snp->srcu_gp_seq_needed_exp = gpseq;
		WRITE_ONCE(snp->srcu_gp_seq_needed_exp, gpseq);
		mask = snp->srcu_data_have_cbs[idx];
		snp->srcu_data_have_cbs[idx] = 0;
		spin_unlock_irq_rcu_node(snp);
		@@ -660,7 +660,7 @@ static void srcu_funnel_gp_start(struct srcu_struct ssp, struct srcu_data sdp,
		if (snp == sdp->mynode)
		snp->srcu_data_have_cbs[idx] \|= sdp->grpmask;
		if (!do_norm && ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, s))
		snp->srcu_gp_seq_needed_exp = s;
		WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s);
		spin_unlock_irqrestore_rcu_node(snp, flags);
		}

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