This is a note to let you know that I've just added the patch titled
rcu: Fix batch-limit size problem
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rcu-fix-batch-limit-size-problem.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 878d7439d0f45a95869e417576774673d1fa243f Mon Sep 17 00:00:00 2001
From: Eric Dumazet <[email protected]>
Date: Thu, 18 Oct 2012 04:55:36 -0700
Subject: rcu: Fix batch-limit size problem
From: Eric Dumazet <[email protected]>
commit 878d7439d0f45a95869e417576774673d1fa243f upstream.
Commit 29c00b4a1d9e27 (rcu: Add event-tracing for RCU callback
invocation) added a regression in rcu_do_batch()
Under stress, RCU is supposed to allow to process all items in queue,
instead of a batch of 10 items (blimit), but an integer overflow makes
the effective limit being 1. So, unless there is frequent idle periods
(during which RCU ignores batch limits), RCU can be forced into a
state where it cannot keep up with the callback-generation rate,
eventually resulting in OOM.
This commit therefore converts a few variables in rcu_do_batch() from
int to long to fix this problem, along with the module parameters
controlling the batch limits.
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/rcutree.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -202,13 +202,13 @@ DEFINE_PER_CPU(struct rcu_dynticks, rcu_
.dynticks = ATOMIC_INIT(1),
};
-static int blimit = 10; /* Maximum callbacks per rcu_do_batch.
*/
-static int qhimark = 10000; /* If this many pending, ignore blimit. */
-static int qlowmark = 100; /* Once only this many pending, use blimit. */
-
-module_param(blimit, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
+static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */
+static long qhimark = 10000; /* If this many pending, ignore blimit. */
+static long qlowmark = 100; /* Once only this many pending, use blimit. */
+
+module_param(blimit, long, 0);
+module_param(qhimark, long, 0);
+module_param(qlowmark, long, 0);
int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
@@ -1476,7 +1476,7 @@ static void rcu_do_batch(struct rcu_stat
{
unsigned long flags;
struct rcu_head *next, *list, **tail;
- int bl, count, count_lazy;
+ long bl, count, count_lazy;
/* If no callbacks are ready, just return.*/
if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/rcu-fix-batch-limit-size-problem.patch
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