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authorArnd Bergmann <arnd@arndb.de>2018-12-16 20:48:21 +0100
committerDavid S. Miller <davem@davemloft.net>2018-12-18 15:12:53 -0800
commit809c67059162e7ba85c61a83ad7547b4ffbb1e6e (patch)
tree4fbd0d0a6421a0940ef7a9bbedb1726a40e17b64
parentfa7b28c11bbf389617327ad4dd69bbbbbc16a8b4 (diff)
downloadlinux-809c67059162e7ba85c61a83ad7547b4ffbb1e6e.tar.gz
test_rhashtable: remove semaphore usage
This is one of only two files that initialize a semaphore to a negative value. We don't really need the two semaphores here at all, but can do the same thing in more conventional and more effient way, by using a single waitqueue and an atomic thread counter. This gets us a little bit closer to eliminating classic semaphores from the kernel. It also fixes a corner case where we fail to continue after one of the threads fails to start up. An alternative would be to use a split kthread_create()+wake_up_process() and completely eliminate the separate synchronization. Acked-by: Phil Sutter <phil@nwl.cc> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--lib/test_rhashtable.c32
1 files changed, 19 insertions, 13 deletions
diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
index 82ac39ce5310..6a8ac7626797 100644
--- a/lib/test_rhashtable.c
+++ b/lib/test_rhashtable.c
@@ -20,11 +20,11 @@
#include <linux/module.h>
#include <linux/rcupdate.h>
#include <linux/rhashtable.h>
-#include <linux/semaphore.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/random.h>
#include <linux/vmalloc.h>
+#include <linux/wait.h>
#define MAX_ENTRIES 1000000
#define TEST_INSERT_FAIL INT_MAX
@@ -112,8 +112,8 @@ static struct rhashtable_params test_rht_params_dup = {
.automatic_shrinking = false,
};
-static struct semaphore prestart_sem;
-static struct semaphore startup_sem = __SEMAPHORE_INITIALIZER(startup_sem, 0);
+static atomic_t startup_count;
+static DECLARE_WAIT_QUEUE_HEAD(startup_wait);
static int insert_retry(struct rhashtable *ht, struct test_obj *obj,
const struct rhashtable_params params)
@@ -634,9 +634,12 @@ static int threadfunc(void *data)
int i, step, err = 0, insert_retries = 0;
struct thread_data *tdata = data;
- up(&prestart_sem);
- if (down_interruptible(&startup_sem))
- pr_err(" thread[%d]: down_interruptible failed\n", tdata->id);
+ if (atomic_dec_and_test(&startup_count))
+ wake_up(&startup_wait);
+ if (wait_event_interruptible(startup_wait, atomic_read(&startup_count) == -1)) {
+ pr_err(" thread[%d]: interrupted\n", tdata->id);
+ goto out;
+ }
for (i = 0; i < tdata->entries; i++) {
tdata->objs[i].value.id = i;
@@ -755,7 +758,7 @@ static int __init test_rht_init(void)
pr_info("Testing concurrent rhashtable access from %d threads\n",
tcount);
- sema_init(&prestart_sem, 1 - tcount);
+ atomic_set(&startup_count, tcount);
tdata = vzalloc(array_size(tcount, sizeof(struct thread_data)));
if (!tdata)
return -ENOMEM;
@@ -781,15 +784,18 @@ static int __init test_rht_init(void)
tdata[i].objs = objs + i * entries;
tdata[i].task = kthread_run(threadfunc, &tdata[i],
"rhashtable_thrad[%d]", i);
- if (IS_ERR(tdata[i].task))
+ if (IS_ERR(tdata[i].task)) {
pr_err(" kthread_run failed for thread %d\n", i);
- else
+ atomic_dec(&startup_count);
+ } else {
started_threads++;
+ }
}
- if (down_interruptible(&prestart_sem))
- pr_err(" down interruptible failed\n");
- for (i = 0; i < tcount; i++)
- up(&startup_sem);
+ if (wait_event_interruptible(startup_wait, atomic_read(&startup_count) == 0))
+ pr_err(" wait_event interruptible failed\n");
+ /* count is 0 now, set it to -1 and wake up all threads together */
+ atomic_dec(&startup_count);
+ wake_up_all(&startup_wait);
for (i = 0; i < tcount; i++) {
if (IS_ERR(tdata[i].task))
continue;