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 11/18] rcutorture: Fix rcu_torture_one_read()/rcu_torture_writer() data race
Date: Fri, 14 Feb 2020 16:41:18 -0800 [thread overview]
Message-ID: <20200215004125.16953-5-paulmck@kernel.org> (raw)
In-Reply-To: <20200215003634.GA16227@paulmck-ThinkPad-P72>
From: "Paul E. McKenney" <paulmck@kernel.org>
The ->rtort_pipe_count field in the rcu_torture structure checks for
too-short grace periods, and is therefore read by rcutorture's readers
while being updated by rcutorture's writers. This commit therefore
adds the needed READ_ONCE() and WRITE_ONCE() invocations.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely and due to this being rcutorture.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/rcutorture.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 5efd950..edd9746 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -375,11 +375,12 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp)
{
int i;
- i = rp->rtort_pipe_count;
+ i = READ_ONCE(rp->rtort_pipe_count);
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ WRITE_ONCE(rp->rtort_pipe_count, i + 1);
+ if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
rp->rtort_mbtest = 0;
return true;
}
@@ -1015,7 +1016,8 @@ rcu_torture_writer(void *arg)
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- old_rp->rtort_pipe_count++;
+ WRITE_ONCE(old_rp->rtort_pipe_count,
+ old_rp->rtort_pipe_count + 1);
switch (synctype[torture_random(&rand) % nsynctypes]) {
case RTWS_DEF_FREE:
rcu_torture_writer_state = RTWS_DEF_FREE;
@@ -1291,7 +1293,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
atomic_inc(&n_rcu_torture_mberror);
rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
preempt_disable();
- pipe_count = p->rtort_pipe_count;
+ pipe_count = READ_ONCE(p->rtort_pipe_count);
if (pipe_count > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
--
2.9.5
next prev parent reply other threads:[~2020-02-15 0:41 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-15 0:36 [PATCH tip/core/rcu 0/18] Torture-test updates for v5.7 Paul E. McKenney
2020-02-15 0:36 ` [PATCH tip/core/rcu 01/18] rcutorture: Suppress forward-progress complaints during early boot paulmck
2020-02-15 0:36 ` [PATCH tip/core/rcu 02/18] torture: Make results-directory date format completion-friendly paulmck
2020-02-15 0:36 ` [PATCH tip/core/rcu 03/18] rcutorture: Refrain from callback flooding during boot paulmck
2020-02-15 0:36 ` [PATCH tip/core/rcu 04/18] torture: Forgive -EBUSY from boottime CPU-hotplug operations paulmck
2020-02-15 0:36 ` [PATCH tip/core/rcu 05/18] rcutorture: Allow boottime stall warnings to be suppressed paulmck
2020-02-15 0:36 ` [PATCH tip/core/rcu 06/18] rcutorture: Suppress boottime bad-sequence warnings paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 07/18] torture: Allow disabling of boottime CPU-hotplug torture operations paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 08/18] rcutorture: Add 100-CPU configuration paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 09/18] rcutorture: Summarize summary of build and run results paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 10/18] rcutorture: Make kvm-find-errors.sh abort on bad directory paulmck
2020-02-15 0:41 ` paulmck [this message]
2020-02-15 0:41 ` [PATCH tip/core/rcu 12/18] rcutorture: Fix stray access to rcu_fwd_cb_nodelay paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 13/18] rcutorture: Add READ_ONCE() to rcu_torture_count and rcu_torture_batch paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 14/18] rcutorture: Annotation lockless accesses to rcu_torture_current paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 15/18] rcuperf: Measure memory footprint during kfree_rcu() test paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 16/18] rcutorture: Make rcu_torture_barrier_cbs() post from corresponding CPU paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 17/18] rcutorture: Manually clean up after rcu_barrier() failure paulmck
2020-02-15 0:41 ` [PATCH tip/core/rcu 18/18] rcutorture: Set KCSAN Kconfig options to detect more data races paulmck
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