From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Andrea Arcangeli <aarcange@redhat.com>,
peterx@redhat.com, Andrew Morton <akpm@linux-foundation.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Axel Rasmussen <axelrasmussen@google.com>
Subject: [PATCH v2 2/5] userfaultfd/selftests: Remove the time() check on delayed uffd
Date: Mon, 12 Apr 2021 19:27:50 -0400 [thread overview]
Message-ID: <20210412232753.1012412-3-peterx@redhat.com> (raw)
In-Reply-To: <20210412232753.1012412-1-peterx@redhat.com>
There seems to have no guarantee that time() will return the same for the two
calls even if there's no delay, e.g. when a fault is accidentally crossing the
changing of a second. Meanwhile, this message is also not helping that much
since delay could happen with a lot of reasons, e.g., schedule latency of
resolving thread. It may not mean an issue with uffd.
Neither do I saw this error triggered either in the past runs. Even if it
triggers, it'll be drown in all the rest of test logs. Remove it.
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
tools/testing/selftests/vm/userfaultfd.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index ce23db8eec26..5cae66e27171 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -395,7 +395,6 @@ static void *locking_thread(void *arg)
unsigned long long count;
char randstate[64];
unsigned int seed;
- time_t start;
if (bounces & BOUNCE_RANDOM) {
seed = (unsigned int) time(NULL) - bounces;
@@ -432,7 +431,6 @@ static void *locking_thread(void *arg)
page_nr += 1;
page_nr %= nr_pages;
- start = time(NULL);
if (bounces & BOUNCE_VERIFY) {
count = *area_count(area_dst, page_nr);
if (!count) {
@@ -495,12 +493,6 @@ static void *locking_thread(void *arg)
count++;
*area_count(area_dst, page_nr) = count_verify[page_nr] = count;
pthread_mutex_unlock(area_mutex(area_dst, page_nr));
-
- if (time(NULL) - start > 1)
- fprintf(stderr,
- "userfault too slow %ld "
- "possible false positive with overcommit\n",
- time(NULL) - start);
}
return NULL;
--
2.26.2
next prev parent reply other threads:[~2021-04-12 23:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 23:27 [PATCH v2 0/5] userfaultfd/selftests: A few cleanups Peter Xu
2021-04-12 23:27 ` [PATCH v2 1/5] userfaultfd/selftests: Use user mode only Peter Xu
2021-04-12 23:27 ` Peter Xu [this message]
2021-04-12 23:27 ` [PATCH v2 3/5] userfaultfd/selftests: Dropping VERIFY check in locking_thread Peter Xu
2021-04-12 23:27 ` [PATCH v2 4/5] userfaultfd/selftests: Only dump counts if mode enabled Peter Xu
2021-04-12 23:27 ` [PATCH v2 5/5] userfaultfd/selftests: Unify error handling Peter Xu
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