[PATCH v2 4/4] rhashtable-test: allow to retry even if -ENOMEM was returned

Phil Sutter
2015-11-20T17:19:26Z

This is rather a hack to expose the current issue with rhashtable to
under high pressure sometimes return -ENOMEM even though system memory
is not exhausted and a consecutive insert may succeed.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
lib/test_rhashtable.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 6fa77b3..270bf72 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -52,6 +52,10 @@ static int tcount = 10;
module_param(tcount, int, 0);
MODULE_PARM_DESC(tcount, "Number of threads to spawn (default: 10)");

+static bool enomem_retry = false;
+module_param(enomem_retry, bool, 0);
+MODULE_PARM_DESC(enomem_retry, "Retry insert even if -ENOMEM was returned (default: off)");
+
struct test_obj {
int value;
struct rhash_head node;
@@ -79,14 +83,22 @@ static struct semaphore startup_sem = __SEMAPHORE_INITIALIZER(startup_sem, 0);
static int insert_retry(struct rhashtable *ht, struct rhash_head *obj,
const struct rhashtable_params params)
{
- int err, retries = -1;
+ int err, retries = -1, enomem_retries = 0;

do {
retries++;
cond_resched();
err = rhashtable_insert_fast(ht, obj, params);
+ if (err == -ENOMEM && enomem_retry) {
+ enomem_retries++;
+ err = -EBUSY;
+ }
} while (err == -EBUSY);

+ if (enomem_retries)
+ pr_info(" %u insertions retried after -ENOMEM\n",
+ enomem_retries);
+
return err ? : retries;
}

--
2.1.2