From: Elijah Newren <newren@xxxxxxxxx> Several tests wanted to verify that files were actually modified by a merge, which it would do by checking that the mtime was updated. In order to avoid problems with the merge completing so fast that the mtime at the beginning and end of the operation was the same, these tests would first set the mtime of a file to something "old". This "old" value was usually determined as current system clock minus one second, truncated to the nearest integer. Unfortunately, it appears the system clock and filesystem clock are different and comparing across the two runs into race problems resulting in flaky tests. >From https://stackoverflow.com/questions/14392975/timestamp-accuracy-on-ext4-sub-millsecond: date will call the gettimeofday system call which will always return the most accurate time available based on the cached kernel time, adjusted by the CPU cycle time if available to give nanosecond resolution. The timestamps stored in the file system however, are only based on the cached kernel time. ie The time calculated at the last timer interrupt. and from https://apenwarr.ca/log/20181113: Does mtime get set to >= the current time? No, this depends on clock granularity. For example, gettimeofday() can return times in microseconds on my system, but ext4 rounds timestamps down to the previous ~10ms (but not exactly 10ms) increment, with the surprising result that a newly-created file is almost always created in the past: $ python -c " import os, time t0 = time.time() open('testfile', 'w').close() print os.stat('testfile').st_mtime - t0 " -0.00234484672546 So, instead of trying to compare across what are effectively two different clocks, just avoid using the system clock. Any new updates to files have to give an mtime at least as big as what is already in the file, so define "old" as one second before the mtime found in the file before the merge starts. Also, clarify in one test where we check the mtime of different files that it really was intentional. I totally forgot the reasons for that and assumed it was a bug when asked. Reported-by: SZEDER Gábor <szeder.dev@xxxxxxxxx> Signed-off-by: Elijah Newren <newren@xxxxxxxxx> --- t6022, t6046: fix flaky files-are-updated checks Who knew that the system clock and the filesystem clock were apparently different things, causing mtime comparisons to be flaky? Definitely not me. Fix the flaky tests that SZEDER reported and helped track down the cause of. Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-725%2Fnewren%2Ftest-cleanup-more-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-725/newren/test-cleanup-more-v1 Pull-Request: https://github.com/git/git/pull/725 t/t6022-merge-rename.sh | 19 ++++++++++--------- t/t6046-merge-skip-unneeded-updates.sh | 21 +++++++-------------- 2 files changed, 17 insertions(+), 23 deletions(-) diff --git a/t/t6022-merge-rename.sh b/t/t6022-merge-rename.sh index d97cf48495b..23d51c55c8b 100755 --- a/t/t6022-merge-rename.sh +++ b/t/t6022-merge-rename.sh @@ -243,8 +243,7 @@ test_expect_success 'merge of identical changes in a renamed file' ' git reset --hard && git checkout change+rename && - test-tool chmtime =31337 B && - test-tool chmtime --get B >old-mtime && + test-tool chmtime --get -1 B >old-mtime && GIT_MERGE_VERBOSITY=3 git merge change >out && test-tool chmtime --get B >new-mtime && @@ -253,10 +252,12 @@ test_expect_success 'merge of identical changes in a renamed file' ' git reset --hard HEAD^ && git checkout change && - test-tool chmtime =-1 M && - test-tool chmtime --get M >old-mtime && + # A will be renamed to B; we check mtimes and file presence + test_path_is_missing B && + test-tool chmtime --get -1 A >old-mtime && GIT_MERGE_VERBOSITY=3 git merge change+rename >out && + test_path_is_missing A && test-tool chmtime --get B >new-mtime && test $(cat old-mtime) -lt $(cat new-mtime) ' @@ -645,7 +646,7 @@ test_expect_success 'setup avoid unnecessary update, normal rename' ' test_expect_success 'avoid unnecessary update, normal rename' ' git checkout -q avoid-unnecessary-update-1^0 && - test-tool chmtime --get =1000000000 rename >expect && + test-tool chmtime --get -1 rename >expect && git merge merge-branch-1 && test-tool chmtime --get rename >actual && test_cmp expect actual # "rename" should have stayed intact @@ -677,7 +678,7 @@ test_expect_success 'setup to test avoiding unnecessary update, with D/F conflic test_expect_success 'avoid unnecessary update, with D/F conflict' ' git checkout -q avoid-unnecessary-update-2^0 && - test-tool chmtime --get =1000000000 df >expect && + test-tool chmtime --get -1 df >expect && git merge merge-branch-2 && test-tool chmtime --get df >actual && test_cmp expect actual # "df" should have stayed intact @@ -708,7 +709,7 @@ test_expect_success 'setup avoid unnecessary update, dir->(file,nothing)' ' test_expect_success 'avoid unnecessary update, dir->(file,nothing)' ' git checkout -q master^0 && - test-tool chmtime --get =1000000000 df >expect && + test-tool chmtime --get -1 df >expect && git merge side && test-tool chmtime --get df >actual && test_cmp expect actual # "df" should have stayed intact @@ -737,7 +738,7 @@ test_expect_success 'setup avoid unnecessary update, modify/delete' ' test_expect_success 'avoid unnecessary update, modify/delete' ' git checkout -q master^0 && - test-tool chmtime --get =1000000000 file >expect && + test-tool chmtime --get -1 file >expect && test_must_fail git merge side && test-tool chmtime --get file >actual && test_cmp expect actual # "file" should have stayed intact @@ -765,7 +766,7 @@ test_expect_success 'setup avoid unnecessary update, rename/add-dest' ' test_expect_success 'avoid unnecessary update, rename/add-dest' ' git checkout -q master^0 && - test-tool chmtime --get =1000000000 newfile >expect && + test-tool chmtime --get -1 newfile >expect && git merge side && test-tool chmtime --get newfile >actual && test_cmp expect actual # "file" should have stayed intact diff --git a/t/t6046-merge-skip-unneeded-updates.sh b/t/t6046-merge-skip-unneeded-updates.sh index 962030ecdb6..c7d0abb4ca3 100755 --- a/t/t6046-merge-skip-unneeded-updates.sh +++ b/t/t6046-merge-skip-unneeded-updates.sh @@ -71,8 +71,7 @@ test_expect_success '1a-L: Modify(A)/Modify(B), change on B subset of A' ' git checkout A^0 && - test-tool chmtime =-1 b && - test-tool chmtime --get b >old-mtime && + test-tool chmtime --get -1 b >old-mtime && GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err && @@ -102,8 +101,7 @@ test_expect_success '1a-R: Modify(A)/Modify(B), change on B subset of A' ' git checkout B^0 && - test-tool chmtime =-1 b && - test-tool chmtime --get b >old-mtime && + test-tool chmtime --get -1 b >old-mtime && GIT_MERGE_VERBOSITY=3 git merge -s recursive A^0 >out 2>err && # Make sure b WAS updated @@ -198,8 +196,7 @@ test_expect_success '2a-R: Modify/rename, merge into rename side' ' git checkout B^0 && - test-tool chmtime =-1 c && - test-tool chmtime --get c >old-mtime && + test-tool chmtime --get -1 c >old-mtime && GIT_MERGE_VERBOSITY=3 git merge -s recursive A^0 >out 2>err && # Make sure c WAS updated @@ -266,8 +263,7 @@ test_expect_success '2b-L: Rename+Mod(A)/Mod(B), B mods subset of A' ' git checkout A^0 && - test-tool chmtime =-1 c && - test-tool chmtime --get c >old-mtime && + test-tool chmtime --get -1 c >old-mtime && GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err && test_must_be_empty err && @@ -373,8 +369,7 @@ test_expect_success '2c: Modify b & add c VS rename b->c' ' git checkout A^0 && - test-tool chmtime =-1 c && - test-tool chmtime --get c >old-mtime && + test-tool chmtime --get -1 c >old-mtime && GIT_MERGE_VERBOSITY=3 && export GIT_MERGE_VERBOSITY && test_must_fail git merge -s recursive B^0 >out 2>err && @@ -679,8 +674,7 @@ test_expect_failure '4a: Change on A, change on B subset of A, dirty mods presen git checkout A^0 && echo "File rewritten" >b && - test-tool chmtime =-1 b && - test-tool chmtime --get b >old-mtime && + test-tool chmtime --get -1 b >old-mtime && GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err && @@ -747,8 +741,7 @@ test_expect_success '4b: Rename+Mod(A)/Mod(B), change on B subset of A, dirty mo git checkout A^0 && echo "File rewritten" >c && - test-tool chmtime =-1 c && - test-tool chmtime --get c >old-mtime && + test-tool chmtime --get -1 c >old-mtime && GIT_MERGE_VERBOSITY=3 git merge -s recursive B^0 >out 2>err && base-commit: 30e9940356dc67959877f4b2417da33ebdefbb79 -- gitgitgadget
