The following commit has been merged into the core/rcu branch of tip: Commit-ID: 065a6db12a80fac4eccc37e6bef14b0f4a610f31 Gitweb: https://git.kernel.org/tip/065a6db12a80fac4eccc37e6bef14b0f4a610f31 Author: Paul E. McKenney <[email protected]> AuthorDate: Fri, 03 Jan 2020 15:22:01 -08:00 Committer: Paul E. McKenney <[email protected]> CommitterDate: Mon, 27 Apr 2020 11:01:16 -07:00
rcu: Add READ_ONCE and data_race() to rcu_node ->boost_tasks The rcu_node structure's ->boost_tasks field is read locklessly, so this commit adds the READ_ONCE() to one load in order to avoid destructive compiler optimizations. The other load is from a diagnostic print, so data_race() suffices. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/tree_plugin.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 35d77db..ed6bb46 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -760,7 +760,7 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck) pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx\n", __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext); pr_info("%s: ->gp_tasks %p ->boost_tasks %p ->exp_tasks %p\n", - __func__, READ_ONCE(rnp->gp_tasks), rnp->boost_tasks, + __func__, READ_ONCE(rnp->gp_tasks), data_race(rnp->boost_tasks), READ_ONCE(rnp->exp_tasks)); pr_info("%s: ->blkd_tasks", __func__); i = 0; @@ -1036,7 +1036,8 @@ static int rcu_boost_kthread(void *arg) for (;;) { WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_WAITING); trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); - rcu_wait(rnp->boost_tasks || READ_ONCE(rnp->exp_tasks)); + rcu_wait(READ_ONCE(rnp->boost_tasks) || + READ_ONCE(rnp->exp_tasks)); trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_RUNNING); more2boost = rcu_boost(rnp);
