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authorEric Dumazet <edumazet@google.com>2012-10-18 04:55:36 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-12-17 10:37:46 -0800
commit29251de53e1712158c29b3626a008d8b93a6e024 (patch)
treeacbbbf18020a71fd5d01beba87453b70fc24b989
parentd5a79aa30b7e6cd68dfee6a76acbe6c7f7905f51 (diff)
rcu: Fix batch-limit size problem
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 <edumazet@google.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/rcutree.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 4eec66e0350d..62c5e9cf6fcb 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -202,13 +202,13 @@ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
.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. */
+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, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
+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_state *rsp, struct rcu_data *rdp)
{
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)) {