From 809c67059162e7ba85c61a83ad7547b4ffbb1e6e Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Sun, 16 Dec 2018 20:48:21 +0100 Subject: 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 Signed-off-by: Arnd Bergmann Acked-by: Herbert Xu Signed-off-by: David S. Miller --- lib/test_rhashtable.c | 32 +++++++++++++++++++------------- 1 file 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 #include #include -#include #include #include #include #include +#include #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; -- cgit v1.2.3-59-g8ed1b