The patch titled
rcu: Fix barriers
has been added to the -mm tree. Its filename is
rcu-fix-barriers.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: rcu: Fix barriers
From: Dipankar Sarma <dipankar@xxxxxxxxxx>
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@xxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/rcuclassic.c | 2 +-
kernel/rcupdate.c | 11 +++++++++++
2 files changed, 12 insertions(+), 1 deletion(-)
diff -puN kernel/rcuclassic.c~rcu-fix-barriers kernel/rcuclassic.c
--- a/kernel/rcuclassic.c~rcu-fix-barriers
+++ a/kernel/rcuclassic.c
@@ -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
--- a/kernel/rcupdate.c~rcu-fix-barriers
+++ a/kernel/rcupdate.c
@@ -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);
}
_
Patches currently in -mm which might be from dipankar@xxxxxxxxxx are
rcu-split-classic-rcu.patch
rcu-softirq-for-rcu.patch
rcu-fix-barriers.patch
rcu-preemptible-rcu.patch
rcu-debug-trace-for-rcu.patch
rcu-trivial-fixes.patch
-
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