From: Scott Wood <swood@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Juri Lelli <juri.lelli@redhat.com>,
Clark Williams <williams@redhat.com>,
linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org,
Scott Wood <swood@redhat.com>
Subject: [PATCH RT 1/4] rcu: Acquire RCU lock when disabling BHs
Date: Tue, 18 Jun 2019 20:19:05 -0500 [thread overview]
Message-ID: <20190619011908.25026-2-swood@redhat.com> (raw)
In-Reply-To: <20190619011908.25026-1-swood@redhat.com>
A plain local_bh_disable() is documented as creating an RCU critical
section, and (at least) rcutorture expects this to be the case. However,
in_softirq() doesn't block a grace period on PREEMPT_RT, since RCU checks
preempt_count() directly. Even if RCU were changed to check
in_softirq(), that wouldn't allow blocked BH disablers to be boosted.
Fix this by calling rcu_read_lock() from local_bh_disable(), and update
rcu_read_lock_bh_held() accordingly.
Signed-off-by: Scott Wood <swood@redhat.com>
---
include/linux/rcupdate.h | 4 ++++
kernel/rcu/update.c | 4 ++++
kernel/softirq.c | 12 +++++++++---
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index fb267bc04fdf..aca4e5e25ace 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -637,10 +637,12 @@ static inline void rcu_read_unlock(void)
static inline void rcu_read_lock_bh(void)
{
local_bh_disable();
+#ifndef CONFIG_PREEMPT_RT_FULL
__acquire(RCU_BH);
rcu_lock_acquire(&rcu_bh_lock_map);
RCU_LOCKDEP_WARN(!rcu_is_watching(),
"rcu_read_lock_bh() used illegally while idle");
+#endif
}
/*
@@ -650,10 +652,12 @@ static inline void rcu_read_lock_bh(void)
*/
static inline void rcu_read_unlock_bh(void)
{
+#ifndef CONFIG_PREEMPT_RT_FULL
RCU_LOCKDEP_WARN(!rcu_is_watching(),
"rcu_read_unlock_bh() used illegally while idle");
rcu_lock_release(&rcu_bh_lock_map);
__release(RCU_BH);
+#endif
local_bh_enable();
}
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 3700b730ea55..eb653a329e0b 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -307,7 +307,11 @@ int rcu_read_lock_bh_held(void)
return 0;
if (!rcu_lockdep_current_cpu_online())
return 0;
+#ifdef CONFIG_PREEMPT_RT_FULL
+ return lock_is_held(&rcu_lock_map) || irqs_disabled();
+#else
return in_softirq() || irqs_disabled();
+#endif
}
EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 473369122ddd..eb46dd3ff92d 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -121,8 +121,10 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
long soft_cnt;
WARN_ON_ONCE(in_irq());
- if (!in_atomic())
+ if (!in_atomic()) {
local_lock(bh_lock);
+ rcu_read_lock();
+ }
soft_cnt = this_cpu_inc_return(softirq_counter);
WARN_ON_ONCE(soft_cnt == 0);
@@ -155,8 +157,10 @@ void _local_bh_enable(void)
local_irq_restore(flags);
#endif
- if (!in_atomic())
+ if (!in_atomic()) {
+ rcu_read_unlock();
local_unlock(bh_lock);
+ }
}
void _local_bh_enable_rt(void)
@@ -189,8 +193,10 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
WARN_ON_ONCE(count < 0);
local_irq_enable();
- if (!in_atomic())
+ if (!in_atomic()) {
+ rcu_read_unlock();
local_unlock(bh_lock);
+ }
preempt_check_resched();
}
--
1.8.3.1
next prev parent reply other threads:[~2019-06-19 1:19 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-19 1:19 [PATCH RT 0/4] Address rcutorture issues Scott Wood
2019-06-19 1:19 ` Scott Wood [this message]
2019-06-20 20:53 ` [PATCH RT 1/4] rcu: Acquire RCU lock when disabling BHs Paul E. McKenney
2019-06-20 21:06 ` Scott Wood
2019-06-20 21:20 ` Paul E. McKenney
2019-06-20 21:38 ` Scott Wood
2019-06-20 22:16 ` Paul E. McKenney
2019-06-19 1:19 ` [PATCH RT 2/4] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Scott Wood
2019-06-19 1:19 ` [RFC PATCH RT 3/4] rcu: unlock special: Treat irq and preempt disabled the same Scott Wood
2019-06-20 21:10 ` Paul E. McKenney
2019-06-20 21:59 ` Scott Wood
2019-06-20 22:25 ` Paul E. McKenney
2019-06-20 23:08 ` Scott Wood
2019-06-22 0:26 ` Paul E. McKenney
2019-06-22 19:13 ` Paul E. McKenney
2019-06-24 17:40 ` Scott Wood
2019-06-19 1:19 ` [RFC PATCH RT 4/4] rcutorture: Avoid problematic critical section nesting Scott Wood
2019-06-20 21:18 ` Paul E. McKenney
2019-06-20 21:43 ` Scott Wood
2019-06-21 16:38 ` Sebastian Andrzej Siewior
2019-06-21 23:59 ` Paul E. McKenney
2019-06-26 15:08 ` Steven Rostedt
2019-06-26 16:49 ` Scott Wood
2019-06-27 18:00 ` Paul E. McKenney
2019-06-27 20:16 ` Scott Wood
2019-06-27 20:50 ` Paul E. McKenney
2019-06-27 22:46 ` Scott Wood
2019-06-28 0:52 ` Paul E. McKenney
2019-06-28 19:37 ` Scott Wood
2019-06-28 20:24 ` Paul E. McKenney
2019-06-20 19:12 ` [PATCH RT 0/4] Address rcutorture issues Paul E. McKenney
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