From: Paul E. McKenney Date: Fri, 3 Jan 2020 23:44:23 +0000 (-0800) Subject: rcu: Add WRITE_ONCE() to rcu_node ->qsmaskinitnext X-Git-Tag: v5.10.7~2531^2~18^2^2~20 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=105abf82b0a62664edabcd4c5b4d9414c74ef399;p=platform%2Fkernel%2Flinux-rpi.git 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 --- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 9443909..346321a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3379,7 +3379,7 @@ void rcu_cpu_starting(unsigned int cpu) rnp = rdp->mynode; mask = rdp->grpmask; raw_spin_lock_irqsave_rcu_node(rnp, flags); - rnp->qsmaskinitnext |= mask; + WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask); oldmask = rnp->expmaskinitnext; rnp->expmaskinitnext |= mask; oldmask ^= rnp->expmaskinitnext; @@ -3432,7 +3432,7 @@ void rcu_report_dead(unsigned int cpu) rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); raw_spin_lock_irqsave_rcu_node(rnp, flags); } - rnp->qsmaskinitnext &= ~mask; + WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); raw_spin_unlock(&rcu_state.ofl_lock);