From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
Josh Triplett <josh@joshtriplett.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>
Cc: Zqiang <qiang1.zhang@intel.com>, rcu@vger.kernel.org
Subject: [PATCH 6/9] rcu: Permit start_poll_synchronize_rcu_expedited() to be invoked early
Date: Wed, 15 Mar 2023 19:43:46 +0000 [thread overview]
Message-ID: <20230315194349.10798-6-joel@joelfernandes.org> (raw)
In-Reply-To: <20230315194349.10798-1-joel@joelfernandes.org>
From: Zqiang <qiang1.zhang@intel.com>
According to the commit log of the patch that added it to the kernel,
start_poll_synchronize_rcu_expedited() can be invoked very early, as
in long before rcu_init() has been invoked. But before rcu_init(),
the rcu_data structure's ->mynode field has not yet been initialized.
This means that the start_poll_synchronize_rcu_expedited() function's
attempt to set the CPU's leaf rcu_node structure's ->exp_seq_poll_rq
field will result in a segmentation fault.
This commit therefore causes start_poll_synchronize_rcu_expedited() to
set ->exp_seq_poll_rq only after rcu_init() has initialized all CPUs'
rcu_data structures' ->mynode fields. It also removes the check from
the rcu_init() function so that start_poll_synchronize_rcu_expedited(
is unconditionally invoked. Yes, this might result in an unnecessary
boot-time grace period, but this is down in the noise.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
kernel/rcu/tree.c | 5 ++---
kernel/rcu/tree_exp.h | 5 +++--
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e80e8f128c57..90d54571126a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4942,9 +4942,8 @@ void __init rcu_init(void)
else
qovld_calc = qovld;
- // Kick-start any polled grace periods that started early.
- if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1))
- (void)start_poll_synchronize_rcu_expedited();
+ // Kick-start in case any polled grace periods started early.
+ (void)start_poll_synchronize_rcu_expedited();
rcu_test_sync_prims();
}
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 7cc4856da081..5343f32e7d67 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -1066,9 +1066,10 @@ unsigned long start_poll_synchronize_rcu_expedited(void)
if (rcu_init_invoked())
raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags);
if (!poll_state_synchronize_rcu(s)) {
- rnp->exp_seq_poll_rq = s;
- if (rcu_init_invoked())
+ if (rcu_init_invoked()) {
+ rnp->exp_seq_poll_rq = s;
queue_work(rcu_gp_wq, &rnp->exp_poll_wq);
+ }
}
if (rcu_init_invoked())
raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);
--
2.40.0.rc1.284.g88254d51c5-goog
next prev parent reply other threads:[~2023-03-15 19:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-15 19:43 [PATCH 1/9] rcu: Fix set/clear TICK_DEP_BIT_RCU_EXP bitmask race Joel Fernandes (Google)
2023-03-15 19:43 ` [PATCH 2/9] rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check Joel Fernandes (Google)
2023-03-15 19:43 ` [PATCH 3/9] entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up Joel Fernandes (Google)
2023-03-21 14:20 ` [tip: core/urgent] " tip-bot2 for Frederic Weisbecker
2023-03-15 19:43 ` [PATCH 4/9] rcu: Register rcu-lazy shrinker only for CONFIG_RCU_LAZY=y kernels Joel Fernandes (Google)
2023-03-15 23:19 ` Frederic Weisbecker
2023-03-16 2:28 ` Joel Fernandes
2023-03-15 19:43 ` [PATCH 5/9] rcu: Remove never-set needwake assignment from rcu_report_qs_rdp() Joel Fernandes (Google)
2023-03-15 19:43 ` Joel Fernandes (Google) [this message]
2023-03-15 19:43 ` [PATCH 7/9] rcu-tasks: Report stalls during synchronize_srcu() in rcu_tasks_postscan() Joel Fernandes (Google)
2023-03-15 19:43 ` [PATCH 8/9] rcu: Avoid stack overflow due to __rcu_irq_enter_check_tick() being kprobe-ed Joel Fernandes (Google)
2023-03-15 19:43 ` [PATCH 9/9] rcu: Protect rcu_print_task_exp_stall() ->exp_tasks access Joel Fernandes (Google)
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