Re: kern/56828: futex calls in Linux emulation sometimes hang

To: kern-bug-people%netbsd.org@localhost,gnats-admin%netbsd.org@localhost,netbsd-bugs%netbsd.org@localhost,Thomas Klausner <wiz%NetBSD.org@localhost>
Subject: Re: kern/56828: futex calls in Linux emulation sometimes hang
From: Thomas Klausner <wiz%NetBSD.org@localhost>
Date: Sat, 25 Mar 2023 05:45:01 +0000 (UTC)
The following reply was made to PR kern/56828; it has been noted by GNATS.

From: Thomas Klausner <wiz%NetBSD.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/56828: futex calls in Linux emulation sometimes hang
Date: Sat, 25 Mar 2023 06:44:46 +0100

 I compiled
 https://github.com/linux-test-project/ltp/releases/download/20230127/ltp-full-20230127.tar.bz2
 on a CentOS (exact version unknown, sorry) and copied the contents of
 testcases/kernel/syscalls/futex (see
 https://github.com/linux-test-project/ltp/tree/master/testcases/kernel/syscalls/futex)
 to a NetBSD 10.99.2/amd64 system and ran them. The output shows quite
 a number of problems (look for 'failed' and 'broken' below):
 
 *** futex_cmp_requeue01 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_cmp_requeue01.c:194: TINFO: Testing variant: syscall with old kernel spec
 futex_cmp_requeue01.c:103: TINFO: Test 0: waiters: 10, wakes: 3, requeues: 7
 futex_cmp_requeue01.c:126: TINFO: futex_cmp_requeue() returned 3
 futex_cmp_requeue01.c:140: TINFO: children woken, futex0: 0, futex1: 7, spurious wakeups: 0
 futex_cmp_requeue01.c:180: TFAIL: woken up -4, expected range (3, 3)
 futex_cmp_requeue01.c:103: TINFO: Test 1: waiters: 10, wakes: 0, requeues: 10
 futex_cmp_requeue01.c:126: TINFO: futex_cmp_requeue() returned 0
 futex_cmp_requeue01.c:140: TINFO: children woken, futex0: 0, futex1: 10, spurious wakeups: 0
 futex_cmp_requeue01.c:180: TFAIL: woken up -10, expected range (0, 0)
 futex_cmp_requeue01.c:103: TINFO: Test 2: waiters: 10, wakes: 2, requeues: 6
 futex_cmp_requeue01.c:126: TINFO: futex_cmp_requeue() returned 2
 futex_cmp_requeue01.c:140: TINFO: children woken, futex0: 2, futex1: 6, spurious wakeups: 0
 futex_cmp_requeue01.c:180: TFAIL: woken up -4, expected range (2, 2)
 futex_cmp_requeue01.c:103: TINFO: Test 3: waiters: 100, wakes: 50, requeues: 50
 futex_cmp_requeue01.c:126: TINFO: futex_cmp_requeue() returned 50
 futex_cmp_requeue01.c:140: TINFO: children woken, futex0: 0, futex1: 50, spurious wakeups: 0
 futex_cmp_requeue01.c:180: TFAIL: woken up 0, expected range (50, 50)
 futex_cmp_requeue01.c:103: TINFO: Test 4: waiters: 100, wakes: 0, requeues: 70
 futex_cmp_requeue01.c:126: TINFO: futex_cmp_requeue() returned 0
 futex_cmp_requeue01.c:140: TINFO: children woken, futex0: 30, futex1: 70, spurious wakeups: 0
 futex_cmp_requeue01.c:180: TFAIL: woken up -70, expected range (0, 0)
 futex_cmp_requeue01.c:95: TBROK: fork() failed: EAGAIN/EWOULDBLOCK (11)
 tst_test.c:1606: TINFO: Killed the leftover descendant processes
 
 Summary:
 passed   0
 failed   5
 broken   1
 skipped  0
 warnings 0
 
 *** futex_cmp_requeue02 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_cmp_requeue02.c:71: TINFO: Testing variant: syscall with old kernel spec
 futex_cmp_requeue02.c:64: TPASS: futex_cmp_requeue() failed as expected: EINVAL (22)
 futex_cmp_requeue02.c:64: TPASS: futex_cmp_requeue() failed as expected: EINVAL (22)
 futex_cmp_requeue02.c:53: TFAIL: futex_cmp_requeue() succeeded unexpectedly
 
 HINT: You _MAY_ be missing kernel fixes:
 
 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fbe0e839d1e2
 
 HINT: You _MAY_ be vulnerable to CVE(s):
 
 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6927
 
 Summary:
 passed   2
 failed   1
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wait01 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wait01.c:69: TINFO: Testing variant: syscall with old kernel spec
 futex_wait01.c:62: TPASS: futex_wait() passed: ETIMEDOUT (110)
 futex_wait01.c:62: TPASS: futex_wait() passed: EAGAIN/EWOULDBLOCK (11)
 futex_wait01.c:62: TPASS: futex_wait() passed: ETIMEDOUT (110)
 futex_wait01.c:62: TPASS: futex_wait() passed: EAGAIN/EWOULDBLOCK (11)
 
 Summary:
 passed   4
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wait02 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wait02.c:66: TINFO: Testing variant: syscall with old kernel spec
 futex_wait02.c:59: TPASS: futex_wait() woken up
 
 Summary:
 passed   1
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wait03 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wait03.c:63: TINFO: Testing variant: syscall with old kernel spec
 Test timeouted, sending SIGKILL!
 tst_test.c:1612: TINFO: If you are running on slow machine, try exporting LTP_TIMEOUT_MUL > 1
 tst_test.c:1614: TBROK: Test killed! (timeout?)
 
 Summary:
 passed   0
 failed   0
 broken   1
 skipped  0
 warnings 0
 
 *** futex_wait04 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wait04.c:50: TINFO: Testing variant: syscall with old kernel spec
 futex_wait04.c:39: TPASS: futex_wait() returned -1: EAGAIN/EWOULDBLOCK (11)
 
 Summary:
 passed   1
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wait05 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 sh: systemd-detect-virt: not found
 tst_timer_test.c:357: TINFO: CLOCK_MONOTONIC resolution 69ns
 tst_timer_test.c:365: TINFO: prctl(PR_GET_TIMERSLACK) = -1, using 50us
 tst_test.c:1566: TINFO: Updating max runtime to 0h 00m 09s
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 39s
 tst_timer_test.c:379: TINFO: Failed to set zero latency constraint: No such file or directory
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 1000us 500 iterations, threshold 450.01us
 tst_timer_test.c:285: TINFO: Found 500 outliners in [20033,10715] range
 tst_timer_test.c:305: TINFO: min 10715us, max 20033us, median 19998us, trunc mean 19811.95us (discarded 25)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
     10715 | *
     11206 |
     11697 |
     12188 | .
     12679 |
     13170 |
     13661 |
     14152 |
     14643 |
     15134 |
     15625 |
     16116 |
     16607 |
     17098 |
     17589 |
     18080 |
     18571 | +
     19062 | -
     19553 | ********************************************************************
 --------------------------------------------------------------------------------
     491us | 1 sample = 0.14108 '*', 0.28216 '+', 0.56432 '-', non-zero '.'
 
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 2000us 500 iterations, threshold 450.01us
 tst_timer_test.c:285: TINFO: Found 11 outliners in [20014,20001] range
 tst_timer_test.c:305: TINFO: min 11091us, max 20014us, median 19998us, trunc mean 19963.34us (discarded 25)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
     11091 | .
     11561 |
     12031 |
     12501 |
     12971 |
     13441 |
     13911 | .
     14381 |
     14851 |
     15321 |
     15791 |
     16261 |
     16731 |
     17201 |
     17671 |
     18141 |
     18611 | .
     19081 |
     19551 | ********************************************************************
 --------------------------------------------------------------------------------
     470us | 1 sample = 0.13682 '*', 0.27364 '+', 0.54728 '-', non-zero '.'
 
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 5000us 300 iterations, threshold 450.04us
 tst_timer_test.c:305: TINFO: min 19554us, max 20000us, median 19998us, trunc mean 19996.26us (discarded 15)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
     19554 | .
     19578 |
     19602 |
     19626 |
     19650 |
     19674 |
     19698 |
     19722 |
     19746 |
     19770 |
     19794 |
     19818 |
     19842 |
     19866 |
     19890 |
     19914 |
     19938 |
     19962 |
     19986 | ********************************************************************
 --------------------------------------------------------------------------------
      24us | 1 sample = 0.22742 '*', 0.45485 '+', 0.90970 '-', non-zero '.'
 
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 10000us 100 iterations, threshold 450.33us
 tst_timer_test.c:305: TINFO: min 19678us, max 20001us, median 19998us, trunc mean 19994.49us (discarded 5)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
     19678 | +
     19695 |
     19712 |
     19729 |
     19746 |
     19763 |
     19780 |
     19797 |
     19814 |
     19831 |
     19848 |
     19865 |
     19882 |
     19899 |
     19916 |
     19933 |
     19950 |
     19967 |
     19984 | ********************************************************************
     20001 | +
 --------------------------------------------------------------------------------
      17us | 1 sample = 0.69388 '*', 1.38776 '+', 2.77551 '-', non-zero '.'
 
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 25000us 50 iterations, threshold 451.29us
 tst_timer_test.c:305: TINFO: min 39713us, max 40000us, median 39998us, trunc mean 39992.19us (discarded 2)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
     39713 | *-
     39729 |
     39745 |
     39761 |
     39777 |
     39793 |
     39809 |
     39825 |
     39841 |
     39857 |
     39873 |
     39889 |
     39905 |
     39921 |
     39937 |
     39953 |
     39969 |
     39985 | ********************************************************************
 --------------------------------------------------------------------------------
      16us | 1 sample = 1.38776 '*', 2.77551 '+', 5.55102 '-', non-zero '.'
 
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 100000us 10 iterations, threshold 537.00us
 tst_timer_test.c:305: TINFO: min 109716us, max 110001us, median 109999us, trunc mean 109967.78us (discarded 1)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
    109716 | ********+
    109731 |
    109746 |
    109761 |
    109776 |
    109791 |
    109806 |
    109821 |
    109836 |
    109851 |
    109866 |
    109881 |
    109896 |
    109911 |
    109926 |
    109941 |
    109956 |
    109971 |
    109986 | ********************************************************************
    110001 | ********+
 --------------------------------------------------------------------------------
      15us | 1 sample = 8.50000 '*', 17.00000 '+', 34.00000 '-', non-zero '.'
 
 tst_timer_test.c:263: TINFO: futex_wait() sleeping for 1000000us 2 iterations, threshold 4400.00us
 tst_timer_test.c:305: TINFO: min 1009721us, max 1010012us, median 1009721us, trunc mean 1009721.00us (discarded 1)
 tst_timer_test.c:314: TFAIL: futex_wait() slept for too long
 
  Time: us | Frequency
 --------------------------------------------------------------------------------
   1009721 | ********************************************************************
   1009737 |
   1009753 |
   1009769 |
   1009785 |
   1009801 |
   1009817 |
   1009833 |
   1009849 |
   1009865 |
   1009881 |
   1009897 |
   1009913 |
   1009929 |
   1009945 |
   1009961 |
   1009977 |
   1009993 |
   1010009 | ********************************************************************
 --------------------------------------------------------------------------------
      16us | 1 sample = 68.00000 '*', 136.00000 '+', 272.00000 '-', non-zero '.'
 
 
 Summary:
 passed   0
 failed   7
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wait_bitset01 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wait_bitset01.c:99: TINFO: Testing variant: syscall with old kernel spec
 futex_wait_bitset01.c:44: TINFO: testing futex_wait_bitset() timeout with CLOCK_MONOTONIC
 futex_wait_bitset01.c:86: TPASS: futex_wait_bitset() waited 114236us, expected 100010us
 futex_wait_bitset01.c:44: TINFO: testing futex_wait_bitset() timeout with CLOCK_REALTIME
 futex_wait_bitset01.c:86: TPASS: futex_wait_bitset() waited 119960us, expected 100010us
 
 Summary:
 passed   2
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_waitv01 ***
 
 tst_test.c:899: TCONF: The test requires kernel 5.16 or newer
 
 *** futex_waitv02 ***
 
 tst_test.c:899: TCONF: The test requires kernel 5.16 or newer
 
 *** futex_waitv03 ***
 
 tst_test.c:899: TCONF: The test requires kernel 5.16 or newer
 
 *** futex_wake01 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wake01.c:59: TINFO: Testing variant: syscall with old kernel spec
 futex_wake01.c:52: TPASS: futex_wake() passed
 futex_wake01.c:52: TPASS: futex_wake() passed
 futex_wake01.c:52: TPASS: futex_wake() passed
 futex_wake01.c:52: TPASS: futex_wake() passed
 futex_wake01.c:52: TPASS: futex_wake() passed
 futex_wake01.c:52: TPASS: futex_wake() passed
 
 Summary:
 passed   6
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wake02 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wake02.c:134: TINFO: Testing variant: syscall with old kernel spec
 futex_utils.h:69: TINFO: 0 threads sleeping, expected 55
 futex_wake02.c:91: TPASS: futex_wake() woken up 1 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 2 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 3 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 4 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 5 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 6 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 7 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 8 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 9 threads
 futex_wake02.c:91: TPASS: futex_wake() woken up 10 threads
 futex_wake02.c:103: TPASS: futex_wake() woken up 0 threads
 
 Summary:
 passed   11
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wake03 ***
 
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 tst_test.c:1558: TINFO: Timeout per run is 0h 00m 30s
 tst_memutils.c:141: TINFO: oom_score_adj does not exist, skipping the adjustment
 futex_wake03.c:97: TINFO: Testing variant: syscall with old kernel spec
 futex_wake03.c:61: TPASS: futex_wake() woken up 1 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 2 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 3 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 4 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 5 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 6 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 7 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 8 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 9 childs
 futex_wake03.c:61: TPASS: futex_wake() woken up 10 childs
 futex_wake03.c:89: TPASS: futex_wake() woken up 0 children
 
 Summary:
 passed   11
 failed   0
 broken   0
 skipped  0
 warnings 0
 
 *** futex_wake04 ***
 
 tst_test.c:1152: TCONF: Test needs to be run as root
 
 
 Running the last as root just gives:
 
 tst_hugepage.c:34: TCONF: hugetlbfs is not supported
 
 Perhaps these are easier-to-debug cases?
  Thomas
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