From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.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 rcu 3/5] rcu-tasks: Mark ->trc_reader_special.b.need_qs data races
Date: Wed, 21 Jul 2021 13:38:16 -0700 [thread overview]
Message-ID: <20210721203818.3398345-3-paulmck@kernel.org> (raw)
In-Reply-To: <20210721203758.GA3386731@paulmck-ThinkPad-P17-Gen-1>
There are several ->trc_reader_special.b.need_qs data races that are
too low-probability for KCSAN to notice, but which will happen sooner
or later. This commit therefore marks these accesses.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index f6b5320c44849..1cece5e9be9a9 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -850,7 +850,7 @@ static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
/* If we are the last reader, wake up the grace-period kthread. */
void rcu_read_unlock_trace_special(struct task_struct *t, int nesting)
{
- int nq = t->trc_reader_special.b.need_qs;
+ int nq = READ_ONCE(t->trc_reader_special.b.need_qs);
if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) &&
t->trc_reader_special.b.need_mb)
@@ -916,7 +916,7 @@ static void trc_read_check_handler(void *t_in)
// Get here if the task is in a read-side critical section. Set
// its state so that it will awaken the grace-period kthread upon
// exit from that critical section.
- WARN_ON_ONCE(t->trc_reader_special.b.need_qs);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs));
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
reset_ipi:
@@ -968,7 +968,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg)
// state so that it will awaken the grace-period kthread upon exit
// from that critical section.
atomic_inc(&trc_n_readers_need_end); // One more to wait on.
- WARN_ON_ONCE(t->trc_reader_special.b.need_qs);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs));
WRITE_ONCE(t->trc_reader_special.b.need_qs, true);
return true;
}
@@ -1103,7 +1103,7 @@ static void show_stalled_task_trace(struct task_struct *t, bool *firstreport)
".i"[is_idle_task(t)],
".N"[cpu > 0 && tick_nohz_full_cpu(cpu)],
READ_ONCE(t->trc_reader_nesting),
- " N"[!!t->trc_reader_special.b.need_qs],
+ " N"[!!READ_ONCE(t->trc_reader_special.b.need_qs)],
cpu);
sched_show_task(t);
}
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2021-07-21 20:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 20:37 [PATCH rcu 0/5] Tasks-RCU updates for v5.15 Paul E. McKenney
2021-07-21 20:38 ` [PATCH rcu 1/5] rcu-tasks: Add comments explaining task_struct strategy Paul E. McKenney
2021-07-21 20:38 ` [PATCH rcu 2/5] rcu-tasks: Mark ->trc_reader_nesting data races Paul E. McKenney
2021-07-21 20:38 ` Paul E. McKenney [this message]
2021-07-21 20:38 ` [PATCH rcu 4/5] rcu-tasks: Fix synchronize_rcu_rude() typo in comment Paul E. McKenney
2021-07-21 20:38 ` [PATCH rcu 5/5] rcu: Fix macro name CONFIG_TASKS_RCU_TRACE Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210721203818.3398345-3-paulmck@kernel.org \
--to=paulmck@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=dhowells@redhat.com \
--cc=edumazet@google.com \
--cc=fweisbec@gmail.com \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).