From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 05/19] rcu: Add READ_ONCE and data_race() to rcu_node ->boost_tasks
Date: Wed, 15 Apr 2020 10:10:40 -0700 [thread overview]
Message-ID: <20200415171054.9013-5-paulmck@kernel.org> (raw)
In-Reply-To: <20200415171017.GA7821@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@kernel.org>
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 <paulmck@kernel.org>
---
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);
--
2.9.5
next prev parent reply other threads:[~2020-04-15 17:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 17:10 [PATCH tip/core/rcu 0/19] Miscellaneous fixes for v5.8 Paul E. McKenney
2020-04-15 17:10 ` [PATCH tip/core/rcu 01/19] rcu: Add KCSAN stubs paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 02/19] srcu: " paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 03/19] rcu: Mark rcu_state.ncpus to detect concurrent writes paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 04/19] rcu: Add *_ONCE() and data_race() to rcu_node ->exp_tasks plus locking paulmck
2020-04-15 17:10 ` paulmck [this message]
2020-04-15 17:10 ` [PATCH tip/core/rcu 06/19] srcu: Add data_race() to ->srcu_lock_count and ->srcu_unlock_count arrays paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 07/19] rcu: Add WRITE_ONCE() to rcu_node ->boost_tasks paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 08/19] rcu: Use data_race() for RCU CPU stall-warning prints paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 09/19] drm: Make drm_dp_mst_dsc_aux_for_port() safe for old compilers paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 10/19] rcu: Expedite first two FQS scans under callback-overload conditions paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 11/19] rcu: Fix the (t=0 jiffies) false positive paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 12/19] Revert "rculist: Describe variadic macro argument in a Sphinx-compatible way" paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 13/19] rcu: Get rid of some doc warnings in update.c paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 14/19] rcu: Mark rcu_state.gp_seq to detect more concurrent writes paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 15/19] rcu: Replace assigned pointer ret value by corresponding boolean value paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 16/19] rcu: Replace 1 by true paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 17/19] rcu: Convert ULONG_CMP_GE() to time_after() for jiffy comparison paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 18/19] rcu: Convert rcu_initiate_boost() ULONG_CMP_GE() to time_after() paulmck
2020-04-15 17:10 ` [PATCH tip/core/rcu 19/19] rcu: Convert rcu_nohz_full_cpu() ULONG_CMP_LT() to time_before() paulmck
2020-04-15 17:21 ` [PATCH tip/core/rcu 0/19] Miscellaneous fixes for v5.8 Andrew Morton
2020-04-15 17:32 ` Paul E. McKenney
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