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Date:      Wed, 11 Apr 2018 21:00:29 -0700
From:      Eitan Adler <lists@eitanadler.com>
To:        "hackers@freebsd.org" <hackers@freebsd.org>
Subject:   panic: deadlkres: possible deadlock detected for 0xfffff80141b04560,  blocked for 1801695 ticks
Message-ID:  <CAF6rxgmF_aOx-R7nZ%2B6-N70jwtH8pgHXPK3WovHS2V5Aed0qwA@mail.gmail.com>

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How to reproduce?

# kldload sem
# kldunload sem
< wait debug.deadlkres.slptime_threshold seconds >

https://reviews.freebsd.org/P168
Reading symbols from ./kernel/kernel...Reading symbols from
/usr/home/eax/crashes/sem_load_dklres/kernel/kernel.debug...done.
done.

Unread portion of the kernel message buffer:
[29474] panic: deadlkres: possible deadlock detected for
0xfffff80141b04560, blocked for 1801695 ticks
[29474]
[29474] cpuid = 31
[29474] time = 1523493929
[29474] KDB: stack backtrace:
[29474] db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
0xfffffe00a6204960
[29474] vpanic() at vpanic+0x18d/frame 0xfffffe00a62049c0
[29474] panic() at panic+0x43/frame 0xfffffe00a6204a20
[29474] deadlkres() at deadlkres+0x3a6/frame 0xfffffe00a6204a70
[29474] fork_exit() at fork_exit+0x84/frame 0xfffffe00a6204ab0
[29474] fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00a6204ab0
[29474] --- trap 0, rip = 0, rsp = 0, rbp = 0 ---
[29474] KDB: enter: panic

__curthread () at ./machine/pcpu.h:230
230             __asm("movq %%gs:%1,%0" : "=r" (td)
(kgdb) bt
#0  __curthread () at ./machine/pcpu.h:230
#1  doadump (textdump=0x1) at /usr/src/sys/kern/kern_shutdown.c:361
#2  0xffffffff80434f4c in db_fncall_generic (addr=<optimized out>,
rv=<optimized out>, nargs=<optimized out>, args=<optimized out>)
    at /usr/src/sys/ddb/db_command.c:609
#3  db_fncall (dummy1=<optimized out>, dummy2=<optimized out>,
dummy3=<optimized out>, dummy4=<optimized out>) at
/usr/src/sys/ddb/db_command.c:657
#4  0xffffffff80434a99 in db_command (last_cmdp=<optimized out>,
cmd_table=<optimized out>, dopager=<optimized out>) at
/usr/src/sys/ddb/db_command.c:481
#5  0xffffffff80434814 in db_command_loop () at
/usr/src/sys/ddb/db_command.c:534
#6  0xffffffff80437a3f in db_trap (type=<optimized out>,
code=<optimized out>) at /usr/src/sys/ddb/db_main.c:250
#7  0xffffffff80babf53 in kdb_trap (type=0x3, code=0xffff0ff0,
tf=<optimized out>) at /usr/src/sys/kern/subr_kdb.c:697
#8  0xffffffff81024aa8 in trap (frame=0xfffffe00a6204890) at
/usr/src/sys/amd64/amd64/trap.c:548
#9  <signal handler called>
#10 kdb_enter (why=0xffffffff8129f663 "panic", msg=<optimized out>) at
/usr/src/sys/kern/subr_kdb.c:479
#11 0xffffffff80b66b5a in vpanic (fmt=<optimized out>,
ap=0xfffffe00a6204a00) at /usr/src/sys/kern/kern_shutdown.c:826
#12 0xffffffff80b66be3 in panic (fmt=0xffffffff81deab08 <cnputs_mtx>
"5i&\201\377\377\377\377") at /usr/src/sys/kern/kern_shutdown.c:764
#13 0xffffffff80b00466 in deadlkres () at /usr/src/sys/kern/kern_clock.c:288
#14 0xffffffff80b26e34 in fork_exit (callout=0xffffffff80b000c0
<deadlkres>, arg=0x0, frame=0xfffffe00a6204ac0) at
/usr/src/sys/kern/kern_fork.c:1039
#15 <signal handler called>

(kgdb)
#13 0xffffffff80b00466 in deadlkres () at /usr/src/sys/kern/kern_clock.c:288
288             panic("%s: possible deadlock detected for %p, blocked
for %d ticks\n",
(kgdb) info locals
tryl = <optimized out>
slpticks = 0x1b7740
blkticks = 0xdbba0
p = 0xfffff80141b00538
td = <optimized out>
wchan = 0xffffffff81deb2d8 <kld_sx>
tticks = 0x1b7ddf
slptype = <optimized out>
i = <error reading variable i (Cannot access memory at address 0x2)>

(more in the paste)

-- 
Eitan Adler



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