On 12/28/20 12:24 PM, John Baldwin wrote: > I got this panic again today in a VM when quitting a gdb > session after killing a child process via 'kill'. > > panic: Assertion pgrp->pg_jobc > 0 failed at > /git/bhyve/sys/kern/kern_proc.c:816 > cpuid = 1 > time = 1609185862 > KDB: stack backtrace: > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00946547f0 > vpanic() at vpanic+0x181/frame 0xfffffe0094654840 > panic() at panic+0x43/frame 0xfffffe00946548a0 > _refcount_update_saturated() at _refcount_update_saturated/frame > 0xfffffe00946548e0 > killjobc() at killjobc+0x6a6/frame 0xfffffe0094654940 > exit1() at exit1+0x6af/frame 0xfffffe00946549b0 > sys_sys_exit() at sys_sys_exit+0xd/frame 0xfffffe00946549c0 > amd64_syscall() at amd64_syscall+0x12e/frame 0xfffffe0094654af0 > fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe0094654af0 > --- syscall (1, FreeBSD ELF64, sys_sys_exit), rip = 0x8024c8f0a, rsp = > 0x7fffffffe358, rbp = 0x7fffffffe370 --- > KDB: enter: panic > [ thread pid 44034 tid 102484 ] > Stopped at kdb_enter+0x37: movq $0,0x10ab066(%rip) > > From what I can tell, the child process that was killed via 'kill' has > not yet exited and is stuck in ptracestop() from fork(): > > (kgdb) where > #0 sched_switch (td=0xfffffe0094001a00, flags=<optimized out>) at > /git/bhyve/sys/kern/sched_ule.c:2147 > #1 0xffffffff80bf4015 in mi_switch (flags=266) at > /git/bhyve/sys/kern/kern_synch.c:542 > #2 0xffffffff80bfeba5 in thread_suspend_switch (td=<optimized out>, > p=<optimized out>) > at /git/bhyve/sys/kern/kern_thread.c:1477 > #3 0xffffffff80bef04b in ptracestop (td=0xfffffe0094001a00, sig=17, si=0x0) > at /git/bhyve/sys/kern/kern_sig.c:2642 > #4 0xffffffff80ba1a54 in fork_return (td=0xfffffe0094001a00, > frame=0xfffffe0094671b00) > at /git/bhyve/sys/kern/kern_fork.c:1106 > #5 0xffffffff80ba18b0 in fork_exit (callout=0xffffffff80ba1950 > <fork_return>, arg=0xfffffe0094001a00, > frame=0xfffffe0094671b00) at /git/bhyve/sys/kern/kern_fork.c:1069 > #6 <signal handler called> > #7 0x00000008007b71aa in ?? () > > kgdb can't find the panicking process due to the zombproc removal, so I will > have to go work on kgdb to recover from that change. :(
I've come up with a shorter reproducer (original was trying to debug a perl script in OpenSSL's test suite). Compile this program: #include <sys/types.h> #include <sys/wait.h> #include <err.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> int main(void) { pid_t pid, wpid; pid = fork(); if (pid == -1) err(1, "fork"); if (pid == 0) { printf("I'm in the child\n"); exit(1); } printf("I'm in the parent\n"); wpid = waitpid(pid, NULL, 0); if (wpid < 0) err(1, "waitpid"); return (0); } Then in gdb do the following: # gdb101 ./forktest ... (gdb) catch fork Catchpoint 1 (fork) (gdb) r Starting program: /mnt/forktest/forktest Catchpoint 1 (forked process 830), _fork () at _fork.S:4 4 _fork.S: No such file or directory. (gdb) kill Kill the program being debugged? (y or n) y [Inferior 1 (process 828) killed] (gdb) quit <panic> -- John Baldwin _______________________________________________ freebsd-current@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"