Hello, I checked the backtrace of a crashed dhcpd running on 4.4.1-2.1ubuntu5.
(gdb) info threads Id Target Id Frame * 1 Thread 0x7fb4ddecb700 (LWP 3170) __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50 2 Thread 0x7fb4dd6ca700 (LWP 3171) __lll_lock_wait (futex=futex@entry=0x7fb4de6d2028, private=0) at lowlevellock.c:52 3 Thread 0x7fb4de6cc700 (LWP 3169) futex_wake (private=<optimized out>, processes_to_wake=1, futex_word=<optimized out>) at ../sysdeps/nptl/futex-internal.h:364 4 Thread 0x7fb4de74f740 (LWP 3148) futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x7fb4de6cd0d0) at ../sysdeps/nptl/futex-internal.h:183 (gdb) frame 2 #2 0x00007fb4dec85985 in isc_assertion_failed (file=file@entry=0x7fb4decd8878 "../../../../lib/isc/unix/socket.c", line=line@entry=3361, type=type@entry=isc_assertiontype_insist, cond=cond@entry=0x7fb4decda033 "!sock->pending_send") at ../../../lib/isc/assertions.c:52 (gdb) bt #1 0x00007fb4deaa7859 in __GI_abort () at abort.c:79 #2 0x00007fb4dec85985 in isc_assertion_failed (file=file@entry=0x7fb4decd8878 "../../../../lib/isc/unix/socket.c", line=line@entry=3361, type=type@entry=isc_assertiontype_insist, cond=cond@entry=0x7fb4decda033 "!sock->pending_send") at ../../../lib/isc/assertions.c:52 #3 0x00007fb4decc17e1 in dispatch_send (sock=0x7fb4de6d4990) at ../../../../lib/isc/unix/socket.c:4041 #4 process_fd (writeable=<optimized out>, readable=<optimized out>, fd=11, manager=0x7fb4de6d0010) at ../../../../lib/isc/unix/socket.c:4054 #5 process_fds (writefds=<optimized out>, readfds=0x7fb4de6d1090, maxfd=13, manager=0x7fb4de6d0010) at ../../../../lib/isc/unix/socket.c:4211 #6 watcher (uap=0x7fb4de6d0010) at ../../../../lib/isc/unix/socket.c:4397 #7 0x00007fb4dea68609 in start_thread (arg=<optimized out>) at pthread_create.c:477 #8 0x00007fb4deba4103 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 (gdb) frame 3 #3 0x00007fb4decc17e1 in dispatch_send (sock=0x7fb4de6d4990) at ../../../../lib/isc/unix/socket.c:4041 4041 in ../../../../lib/isc/unix/socket.c (gdb) p sock->pending_send $2 = 1 The code is crashing on this assertion: https://gitlab.isc.org/isc-projects/bind9/-/blob/v9_11_3/lib/isc/unix/socket.c#L3364 This was already reported and marked as fixed in debian (?) via [0] ""Now if a wakeup event occurres the socket would be dispatched for processing regardless which kind of event (timer?) triggered the wakeup. At least I did not find any sanity checks in process_fds() except SOCK_DEAD(sock). This leads to the following situation: The sock is not dead yet but it is still pending when it is dispatched again. I would now check sock->pending_send before calling dispatch_send().This would at least prevent the assertion failure - well knowing that the situation described above ( not dead but still pending and alerting ) is not a very pleasant one - until someone comes up with a better solution. """ https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=430065#20 ** Follow up questions: 0) The reproducer doesn't seems consistent and seems to be related to a race condition associated with a internal timer/futex. 1) Can anyone confirm that a pristine upstream 4.4.1 doesn't reproduces the issue? ** Bug watch added: Debian Bug tracker #430065 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=430065 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to isc-dhcp in Ubuntu. https://bugs.launchpad.net/bugs/1872118 Title: DHCP Cluster crashes after a few hours Status in DHCP: New Status in bind9-libs package in Ubuntu: New Status in isc-dhcp package in Ubuntu: Confirmed Status in bind9-libs source package in Focal: New Status in isc-dhcp source package in Focal: New Status in bind9-libs source package in Groovy: New Status in isc-dhcp source package in Groovy: Confirmed Bug description: I have a pair of DHCP serevrs running in a cluster on ubuntu 20.04, All worked perfectly until recently, when they started stopping with code=killed, status=6/ABRT. This is being fixed by https://bugs.launchpad.net/bugs/1870729 However now one stops after a few hours with the following errors. One can stay on line but not both. Syslog shows Apr 10 17:20:15 dhcp-primary sh[6828]: ../../../../lib/isc/unix/socket.c:3361: INSIST(!sock->pending_send) failed, back trace Apr 10 17:20:15 dhcp-primary sh[6828]: #0 0x7fbe78702a4a in ?? Apr 10 17:20:15 dhcp-primary sh[6828]: #1 0x7fbe78702980 in ?? Apr 10 17:20:15 dhcp-primary sh[6828]: #2 0x7fbe7873e7e1 in ?? Apr 10 17:20:15 dhcp-primary sh[6828]: #3 0x7fbe784e5609 in ?? Apr 10 17:20:15 dhcp-primary sh[6828]: #4 0x7fbe78621103 in ?? nothing in kern.log apport.log shows ERROR: apport (pid 6850) Fri Apr 10 17:20:15 2020: called for pid 6828, signal 6, core limit 0, dump mode 2 ERROR: apport (pid 6850) Fri Apr 10 17:20:15 2020: not creating core for pid with dump mode of 2 ERROR: apport (pid 6850) Fri Apr 10 17:20:15 2020: executable: /usr/sbin/dhcpd (command line "dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf") ERROR: apport (pid 6850) Fri Apr 10 17:20:15 2020: is_closing_session(): no DBUS_SESSION_BUS_ADDRESS in environment ERROR: apport (pid 6850) Fri Apr 10 17:20:15 2020: wrote report /var/crash/_usr_sbin_dhcpd.0.crash /var/crash/_usr_sbin_dhcpd.0.crash shows ProblemType: Crash Architecture: amd64 CrashCounter: 1 Date: Fri Apr 10 17:20:15 2020 DistroRelease: Ubuntu 20.04 ExecutablePath: /usr/sbin/dhcpd ExecutableTimestamp: 1586210315 ProcCmdline: dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf ProcEnviron: Error: [Errno 13] Permission denied: 'environ' ProcMaps: Error: [Errno 13] Permission denied: 'maps' ProcStatus: Name: dhcpd Umask: 0022 State: D (disk sleep) Tgid: 6828 Ngid: 0 Pid: 6828 PPid: 1 TracerPid: 0 Uid: 113 113 113 113 Gid: 118 118 118 118 FDSize: 128 Groups: NStgid: 6828 NSpid: 6828 NSpgid: 6828 NSsid: 6828 VmPeak: 236244 kB VmSize: 170764 kB VmLck: 0 kB VmPin: 0 kB VmHWM: 12064 kB VmRSS: 12064 kB RssAnon: 5940 kB RssFile: 6124 kB RssShmem: 0 kB VmData: 30792 kB VmStk: 132 kB VmExe: 592 kB VmLib: 5424 kB VmPTE: 76 kB VmSwap: 0 kB HugetlbPages: 0 kB CoreDumping: 1 THP_enabled: 1 Threads: 4 SigQ: 0/7609 SigPnd: 0000000000000000 ShdPnd: 0000000000000000 SigBlk: 0000000000000000 SigIgn: 0000000000001000 SigCgt: 0000000180000000 CapInh: 0000000000000000 CapPrm: 0000000000000000 CapEff: 0000000000000000 CapBnd: 0000003fffffffff CapAmb: 0000000000000000 NoNewPrivs: 0 Seccomp: 0 Speculation_Store_Bypass: thread vulnerable Cpus_allowed: 3 Cpus_allowed_list: 0-1 Mems_allowed: 00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,0000 0000,00000000,00000000,00000001 Mems_allowed_list: 0 voluntary_ctxt_switches: 111 nonvoluntary_ctxt_switches: 144 Signal: 6 Uname: Linux 5.4.0-21-generic x86_64 UserGroups: To manage notifications about this bug go to: https://bugs.launchpad.net/dhcp/+bug/1872118/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp