From: "tip-bot2 for Frederic Weisbecker" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
stable@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: [tip: sched/core] rcu/nocb: Perform deferred wake up before last idle's need_resched() check
Date: Wed, 17 Feb 2021 13:17:31 -0000 [thread overview]
Message-ID: <161356785161.20312.14972284804114619107.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210131230548.32970-3-frederic@kernel.org>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 43789ef3f7d61aa7bed0cb2764e588fc990c30ef
Gitweb: https://git.kernel.org/tip/43789ef3f7d61aa7bed0cb2764e588fc990c30ef
Author: Frederic Weisbecker <frederic@kernel.org>
AuthorDate: Mon, 01 Feb 2021 00:05:45 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 17 Feb 2021 14:12:43 +01:00
rcu/nocb: Perform deferred wake up before last idle's need_resched() check
Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP
kthread (rcuog) to be serviced.
Usually a local wake up happening while running the idle task is handled
in one of the need_resched() checks carefully placed within the idle
loop that can break to the scheduler.
Unfortunately the call to rcu_idle_enter() is already beyond the last
generic need_resched() check and we may halt the CPU with a resched
request unhandled, leaving the task hanging.
Fix this with splitting the rcuog wakeup handling from rcu_idle_enter()
and place it before the last generic need_resched() check in the idle
loop. It is then assumed that no call to call_rcu() will be performed
after that in the idle loop until the CPU is put in low power mode.
Fixes: 96d3fd0d315a (rcu: Break call_rcu() deadlock involving scheduler and perf)
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210131230548.32970-3-frederic@kernel.org
---
include/linux/rcupdate.h | 2 ++
kernel/rcu/tree.c | 3 ---
kernel/rcu/tree_plugin.h | 5 +++++
kernel/sched/idle.c | 1 +
4 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index fd02c5f..36c2119 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -110,8 +110,10 @@ static inline void rcu_user_exit(void) { }
#ifdef CONFIG_RCU_NOCB_CPU
void rcu_init_nohz(void);
+void rcu_nocb_flush_deferred_wakeup(void);
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
static inline void rcu_init_nohz(void) { }
+static inline void rcu_nocb_flush_deferred_wakeup(void) { }
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
/**
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 63032e5..82838e9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -671,10 +671,7 @@ static noinstr void rcu_eqs_enter(bool user)
*/
void rcu_idle_enter(void)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
lockdep_assert_irqs_disabled();
- do_nocb_deferred_wakeup(rdp);
rcu_eqs_enter(false);
}
EXPORT_SYMBOL_GPL(rcu_idle_enter);
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 7e291ce..d5b38c2 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2187,6 +2187,11 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
do_nocb_deferred_wakeup_common(rdp);
}
+void rcu_nocb_flush_deferred_wakeup(void)
+{
+ do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data));
+}
+
void __init rcu_init_nohz(void)
{
int cpu;
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 305727e..7199e6f 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -285,6 +285,7 @@ static void do_idle(void)
}
arch_cpu_idle_enter();
+ rcu_nocb_flush_deferred_wakeup();
/*
* In poll mode we reenable interrupts and spin. Also if we
next prev parent reply other threads:[~2021-02-17 13:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-31 23:05 [PATCH 0/5] rcu/sched: Fix ignored rescheduling after rcu_eqs_enter() v4 Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 1/5] rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 2/5] rcu/nocb: Perform deferred wake up before last idle's need_resched() check Frederic Weisbecker
2021-02-08 14:45 ` Peter Zijlstra
2021-02-08 14:53 ` Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker [this message]
2021-01-31 23:05 ` [PATCH 3/5] rcu/nocb: Trigger self-IPI on late deferred wake up before user resume Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 4/5] entry: Explicitly flush pending rcuog wakeup before last rescheduling point Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
2021-01-31 23:05 ` [PATCH 5/5] entry/kvm: " Frederic Weisbecker
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Frederic Weisbecker
2021-02-17 13:17 ` tip-bot2 for Frederic Weisbecker
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=161356785161.20312.14972284804114619107.tip-bot2@tip-bot2 \
--to=tip-bot2@linutronix.de \
--cc=frederic@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=stable@vger.kernel.org \
--cc=x86@kernel.org \
/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).