+ userfaultfd-selftests-remove-the-time-check-on-delayed-uffd.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: userfaultfd/selftests: remove the time() check on delayed uffd
has been added to the -mm tree.  Its filename is
     userfaultfd-selftests-remove-the-time-check-on-delayed-uffd.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-selftests-remove-the-time-check-on-delayed-uffd.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-selftests-remove-the-time-check-on-delayed-uffd.patch

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------------------------------------------------------
From: Peter Xu <peterx@redhat.com>
Subject: userfaultfd/selftests: remove the time() check on delayed uffd

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.

Link: https://lkml.kernel.org/r/20210412232753.1012412-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Wang Qing <wangqing@vivo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/vm/userfaultfd.c |    8 --------
 1 file changed, 8 deletions(-)

--- a/tools/testing/selftests/vm/userfaultfd.c~userfaultfd-selftests-remove-the-time-check-on-delayed-uffd
+++ a/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;
_

Patches currently in -mm which might be from peterx@redhat.com are

mm-hugetlb-fix-f_seal_future_write.patch
mm-hugetlb-fix-cow-where-page-writtable-in-child.patch
mm-gup_benchmark-support-threading.patch
userfaultfd-selftests-use-user-mode-only.patch
userfaultfd-selftests-remove-the-time-check-on-delayed-uffd.patch
userfaultfd-selftests-dropping-verify-check-in-locking_thread.patch
userfaultfd-selftests-only-dump-counts-if-mode-enabled.patch
userfaultfd-selftests-unify-error-handling.patch
mm-thp-simplify-copying-of-huge-zero-page-pmd-when-fork.patch
mm-userfaultfd-fix-uffd-wp-special-cases-for-fork.patch
mm-userfaultfd-fix-a-few-thp-pmd-missing-uffd-wp-bit.patch
mm-userfaultfd-fail-uffd-wp-registeration-if-not-supported.patch
mm-pagemap-export-uffd-wp-protection-information.patch
userfaultfd-selftests-add-pagemap-uffd-wp-test.patch