+ 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 see 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/20210310004511.51996-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Nadav Amit <nadav.amit@gmail.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
@@ -568,7 +568,6 @@ 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;
@@ -605,7 +604,6 @@ 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) {
@@ -668,12 +666,6 @@ 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

hugetlb-dedup-the-code-to-add-a-new-file_region.patch
hugetlg-break-earlier-in-add_reservation_in_range-when-we-can.patch
mm-introduce-page_needs_cow_for_dma-for-deciding-whether-cow.patch
mm-use-is_cow_mapping-across-tree-where-proper.patch
hugetlb-do-early-cow-when-page-pinned-on-src-mm.patch
hugetlb-pass-vma-into-huge_pte_alloc-and-huge_pmd_share.patch
hugetlb-pass-vma-into-huge_pte_alloc-and-huge_pmd_share-fix.patch
hugetlb-userfaultfd-forbid-huge-pmd-sharing-when-uffd-enabled.patch
hugetlb-userfaultfd-forbid-huge-pmd-sharing-when-uffd-enabled-fix.patch
mm-hugetlb-move-flush_hugetlb_tlb_range-into-hugetlbh.patch
hugetlb-userfaultfd-unshare-all-pmds-for-hugetlbfs-when-register-wp.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