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authorEric Dumazet <edumazet@google.com>2012-10-18 04:55:36 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-11-13 14:07:57 -0800
commit878d7439d0f45a95869e417576774673d1fa243f (patch)
treebf16331cb2e31ab00fe69d91755b7ac6ccb6a7d6
parent62da1921292ef789c23a7bf01d671d7572baf377 (diff)
downloadlinux-878d7439d0f45a95869e417576774673d1fa243f.tar.bz2
rcu: Fix batch-limit size problem
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> Cc: <stable@vger.kernel.org> # 3.2 +
-rw-r--r--kernel/rcutree.c15
1 files changed, 8 insertions, 7 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 93d6871bf7f9..e4c2192b47c8 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -212,13 +212,13 @@ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
#endif
};
-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, 0444);
-module_param(qhimark, int, 0444);
-module_param(qlowmark, int, 0444);
+module_param(blimit, long, 0444);
+module_param(qhimark, long, 0444);
+module_param(qlowmark, long, 0444);
int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
@@ -1791,7 +1791,8 @@ 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, i;
+ long bl, count, count_lazy;
+ int i;
/* If no callbacks are ready, just return.*/
if (!cpu_has_callbacks_ready_to_invoke(rdp)) {