From: Gautham R Shenoy <ego@in.ibm.com>
To: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E McKenney <paulmck@us.ibm.com>,
Dipankar Sarma <dipankar@in.ibm.com>, Ted Tso <tytso@us.ibm.com>,
dvhltc@us.ibm.com, Oleg Nesterov <oleg@tv-sign.ru>,
Andrew Morton <akpm@linux-foundation.org>,
bunk@kernel.org, Josh Triplett <josh@freedesktop.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: [RFC PATCH 3/6] Preempt-RCU: Fix rcu_barrier for preemptive environment
Date: Thu, 13 Dec 2007 22:46:06 +0530 [thread overview]
Message-ID: <20071213171606.GD25981@in.ibm.com> (raw)
In-Reply-To: <20071213170348.GA25981@in.ibm.com>
Preempt-RCU: Fix rcu_barrier for preemptive environment.
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Fix rcu_barrier() to work properly in preemptive kernel environment.
Also, the ordering of callback must be preserved while moving
callbacks to another CPU during CPU hotplug.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcuclassic.c | 2 +-
kernel/rcupdate.c | 10 ++++++++++
2 files changed, 11 insertions(+), 1 deletions(-)
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index 11c16aa..deb2acc 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -371,9 +371,9 @@ static void __rcu_offline_cpu(struct rcu_data *this_rdp,
if (rcp->cur != rcp->completed)
cpu_quiet(rdp->cpu, rcp);
spin_unlock_bh(&rcp->lock);
+ rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
- rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
}
static void rcu_offline_cpu(int cpu)
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 0ccd009..760dfc2 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -115,7 +115,17 @@ void rcu_barrier(void)
mutex_lock(&rcu_barrier_mutex);
init_completion(&rcu_barrier_completion);
atomic_set(&rcu_barrier_cpu_count, 0);
+ /*
+ * The queueing of callbacks in all CPUs must be atomic with
+ * respect to RCU, otherwise one CPU may queue a callback,
+ * wait for a grace period, decrement barrier count and call
+ * complete(), while other CPUs have not yet queued anything.
+ * So, we need to make sure that grace periods cannot complete
+ * until all the callbacks are queued.
+ */
+ rcu_read_lock();
on_each_cpu(rcu_barrier_func, NULL, 0, 1);
+ rcu_read_unlock();
wait_for_completion(&rcu_barrier_completion);
mutex_unlock(&rcu_barrier_mutex);
}
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
next prev parent reply other threads:[~2007-12-13 17:16 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-13 17:03 [RFC PATCH 0/6] RCU: Preemptible-RCU Gautham R Shenoy
2007-12-13 17:14 ` [RFC PATCH 1/6] Preempt-RCU: Use softirq instead of tasklets for RCU Gautham R Shenoy
2007-12-13 17:15 ` [RFC PATCH 2/6] Preempt-RCU: Reorganize RCU code into rcuclassic.c and rcupdate.c Gautham R Shenoy
2007-12-14 14:51 ` Johannes Weiner
2007-12-14 16:12 ` Paul E. McKenney
2007-12-13 17:16 ` Gautham R Shenoy [this message]
2007-12-13 17:16 ` [RFC PATCH 4/6] Preempt-RCU: Implementation Gautham R Shenoy
2008-02-29 4:34 ` Roman Zippel
2008-02-29 4:53 ` Paul E. McKenney
2008-02-29 12:38 ` Roman Zippel
2008-02-29 13:55 ` Steven Rostedt
2008-03-01 19:39 ` Paul E. McKenney
2008-03-01 21:07 ` Steven Rostedt
2008-03-02 3:09 ` Roman Zippel
2008-03-02 3:06 ` Roman Zippel
2008-03-03 18:55 ` Paul E. McKenney
2008-03-04 20:22 ` [PATCH] move PREEMPT_RCU config option back under PREEMPT Paul E. McKenney
2008-03-04 20:55 ` Steven Rostedt
2008-03-05 0:58 ` Paul E. McKenney
2008-03-05 2:06 ` Roman Zippel
2008-03-05 19:00 ` Paul E. McKenney
2008-03-04 20:49 ` [RFC PATCH 4/6] Preempt-RCU: Implementation Roman Zippel
2008-02-29 13:53 ` Steven Rostedt
2008-02-29 14:31 ` Roman Zippel
2007-12-13 17:17 ` [RFC PATCH 5/6] Preempt-RCU: CPU Hotplug handling Gautham R Shenoy
2007-12-13 17:18 ` [RFC PATCH 6/6] Preempt-RCU: Update RCU Documentation Gautham R Shenoy
2007-12-13 20:42 ` Ingo Molnar
2007-12-13 21:06 ` Gautham R Shenoy
2007-12-13 17:36 ` [RFC PATCH 0/6] RCU: Preemptible-RCU Steven Rostedt
2007-12-13 20:42 ` Ingo Molnar
2007-12-13 20:56 ` Steven Rostedt
2007-12-13 21:09 ` Gautham R Shenoy
2007-12-13 20:38 ` Ingo Molnar
2007-12-13 23:41 ` Paul E. McKenney
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