From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org
Cc: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Boqun Feng <boqun.feng@gmail.com>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Joel Fernandes <joel@joelfernandes.org>,
Josh Triplett <josh@joshtriplett.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Zqiang <qiang.zhang1211@gmail.com>
Subject: [PATCH v2 1/6] rcu-tasks: Repair RCU Tasks Trace quiescence check
Date: Fri, 16 Feb 2024 17:27:36 -0800 [thread overview]
Message-ID: <20240217012745.3446231-2-boqun.feng@gmail.com> (raw)
In-Reply-To: <20240217012745.3446231-1-boqun.feng@gmail.com>
From: "Paul E. McKenney" <paulmck@kernel.org>
The context-switch-time check for RCU Tasks Trace quiescence expects
current->trc_reader_special.b.need_qs to be zero, and if so, updates
it to TRC_NEED_QS_CHECKED. This is backwards, because if this value
is zero, there is no RCU Tasks Trace grace period in flight, an thus
no need for a quiescent state. Instead, when a grace period starts,
this field is set to TRC_NEED_QS.
This commit therefore changes the check from zero to TRC_NEED_QS.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
include/linux/rcupdate.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 0746b1b0b663..16f519914415 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -184,9 +184,9 @@ void rcu_tasks_trace_qs_blkd(struct task_struct *t);
do { \
int ___rttq_nesting = READ_ONCE((t)->trc_reader_nesting); \
\
- if (likely(!READ_ONCE((t)->trc_reader_special.b.need_qs)) && \
+ if (unlikely(READ_ONCE((t)->trc_reader_special.b.need_qs) == TRC_NEED_QS) && \
likely(!___rttq_nesting)) { \
- rcu_trc_cmpxchg_need_qs((t), 0, TRC_NEED_QS_CHECKED); \
+ rcu_trc_cmpxchg_need_qs((t), TRC_NEED_QS, TRC_NEED_QS_CHECKED); \
} else if (___rttq_nesting && ___rttq_nesting != INT_MIN && \
!READ_ONCE((t)->trc_reader_special.b.blocked)) { \
rcu_tasks_trace_qs_blkd(t); \
--
2.43.0
next prev parent reply other threads:[~2024-02-17 1:27 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-17 1:27 [PATCH v2 0/6] RCU tasks fixes for v6.9 Boqun Feng
2024-02-17 1:27 ` Boqun Feng [this message]
2024-02-17 1:27 ` [PATCH v2 2/6] rcu-tasks: Add data to eliminate RCU-tasks/do_exit() deadlocks Boqun Feng
2024-02-22 16:54 ` Frederic Weisbecker
2024-02-22 20:46 ` Paul E. McKenney
2024-02-17 1:27 ` [PATCH v2 3/6] rcu-tasks: Initialize " Boqun Feng
2024-02-22 16:21 ` Frederic Weisbecker
2024-02-22 20:41 ` Paul E. McKenney
2024-02-23 11:39 ` Frederic Weisbecker
2024-02-17 1:27 ` [PATCH v2 4/6] rcu-tasks: Maintain lists " Boqun Feng
2024-02-22 16:32 ` Frederic Weisbecker
2024-02-23 12:19 ` Frederic Weisbecker
2024-02-24 0:28 ` Paul E. McKenney
2024-02-17 1:27 ` [PATCH v2 5/6] rcu-tasks: Eliminate deadlocks involving do_exit() and RCU tasks Boqun Feng
2024-02-22 16:46 ` Frederic Weisbecker
2024-02-17 1:27 ` [PATCH v2 6/6] rcu-tasks: Maintain real-time response in rcu_tasks_postscan() Boqun Feng
2024-02-22 17:48 ` Frederic Weisbecker
2024-02-22 20:52 ` Paul E. McKenney
2024-02-22 22:56 ` Paul E. McKenney
2024-02-23 12:17 ` Frederic Weisbecker
2024-02-23 15:14 ` Frederic Weisbecker
2024-02-24 0:23 ` Paul E. McKenney
2024-02-22 16:52 ` [PATCH v2 0/6] RCU tasks fixes for v6.9 Frederic Weisbecker
2024-02-22 22:09 ` Paul E. McKenney
2024-02-23 12:25 ` Frederic Weisbecker
2024-02-24 0:43 ` Paul E. McKenney
2024-02-26 13:56 ` Frederic Weisbecker
2024-02-26 14:37 ` Paul E. McKenney
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