LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Dipankar Sarma <dipankar@in.ibm.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Ingo Molnar <mingo@elte.hu>,
	Paul E McKenney <paulmck@linux.vnet.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [mm PATCH 3/6] RCU: Fix barriers
Date: Tue, 16 Jan 2007 00:54:46 +0530	[thread overview]
Message-ID: <20070115192446.GD32238@in.ibm.com> (raw)
In-Reply-To: <20070115191909.GA32238@in.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: Dipankar Sarma <dipankar@in.ibm.com>
---



diff -puN kernel/rcuclassic.c~rcu-fix-barriers kernel/rcuclassic.c
--- linux-2.6.20-rc3-mm1-rcu/kernel/rcuclassic.c~rcu-fix-barriers	2007-01-15 15:36:47.000000000 +0530
+++ linux-2.6.20-rc3-mm1-rcu-dipankar/kernel/rcuclassic.c	2007-01-15 15:36:47.000000000 +0530
@@ -350,9 +350,9 @@ static void __rcu_offline_cpu(struct rcu
 	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 -puN kernel/rcupdate.c~rcu-fix-barriers kernel/rcupdate.c
--- linux-2.6.20-rc3-mm1-rcu/kernel/rcupdate.c~rcu-fix-barriers	2007-01-15 15:36:47.000000000 +0530
+++ linux-2.6.20-rc3-mm1-rcu-dipankar/kernel/rcupdate.c	2007-01-15 15:36:47.000000000 +0530
@@ -117,7 +117,18 @@ 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
+	 * haven't yet queued anything. So, we need to make sure
+	 * that no grace period happens 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);
 }

_

  parent reply	other threads:[~2007-01-15 19:25 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-15 19:19 [mm PATCH] RCU: various patches Dipankar Sarma
2007-01-15 19:21 ` [mm PATCH 1/6] RCU: split classic rcu Dipankar Sarma
2007-01-16 17:49   ` Paul E. McKenney
2007-01-15 19:22 ` [mm PATCH 2/6] RCU: softirq for RCU Dipankar Sarma
2007-01-16 17:49   ` Paul E. McKenney
2007-01-15 19:24 ` Dipankar Sarma [this message]
2007-01-16 17:53   ` [mm PATCH 3/6] RCU: Fix barriers Paul E. McKenney
2007-01-15 19:28 ` [mm PATCH 4/6] RCU: preemptible RCU Dipankar Sarma
2007-01-24  0:32   ` Andrew Morton
2007-01-26 21:00     ` Dipankar Sarma
2007-01-26 21:25       ` Andrew Morton
2007-01-24  0:38   ` Andrew Morton
2007-01-15 19:30 ` [mm PATCH 5/6] RCU: debug trace for RCU Dipankar Sarma
2007-01-15 19:31 ` [mm PATCH 6/6] RCU: trivial fixes Dipankar Sarma
2007-01-16 17:56   ` Paul E. McKenney

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=20070115192446.GD32238@in.ibm.com \
    --to=dipankar@in.ibm.com \
    --cc=akpm@osdl.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=paulmck@linux.vnet.ibm.com \
    --subject='Re: [mm PATCH 3/6] RCU: Fix barriers' \
    /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

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).