Re: Patched gpsd and /dev/pps0 results in "sleeping thread" kernel panic

From: Warner Losh <imp_at_bsdimp.com>
Date: Tue, 31 Aug 2021 21:25:08 -0600
On Tue, Aug 31, 2021 at 9:13 PM Ian Lepore <ian_at_freebsd.org> wrote:

> On Tue, 2021-08-31 at 21:07 -0600, Warner Losh wrote:
> > On Tue, Aug 31, 2021 at 8:11 PM Craig Leres <leres_at_freebsd.org>
> > wrote:
> >
> > >
> > > On 8/31/21 6:54 PM, Warner Losh wrote:
> > > > Can you post a traceback? We recently tightened up the sleeping
> > > conditions
> > > > and many of the panics are straight forward to fix
> > >
> > > Is this sufficient?
> > >
> >
> > Maybe. I'm guessing that the pps driver isn't setting driver_mtx for
> > the
> > pps_state that it keeps, so when we're sleeping in pps_ioctl we're
> > not
> > dropping the the ppbus lock, which leads to this diagnostic.
> >
> > Warner
> >
> >
>
>
> Exactly so, I've just been digging through the code.  It's not an easy
> fix because the ppbus pps driver doesn't have access to the ppbus mutex
> at the point where it's registering to be a pps driver.
>

I just came to the conclusion that either we'd need to create a call in
ppbus
to set this mutex, or to return its lock...


> Craig, is there any chance you can configure your hardware so that the
> PPS signal is connected to either the CTS or DCD pin of a uart (even
> the same uart that's communicating with the gps receiver should work if
> you use DCD)?  You'll get jitter and accuracy performance comparable to
> the parallel port pin, and avoid this mutex/sleeping problem.
>

That's easier, but depending on the hardware might be harder :(

Warner


> -- Ian
>
>
>
> > >                 Craig
> > >
> > > toc2 4 # kgdb /boot/kernel/kernel /var/crash/vmcore.1
> > > GNU gdb (GDB) 10.2 [GDB v10.2 for FreeBSD]
> > > Copyright (C) 2021 Free Software Foundation, Inc.
> > > License GPLv3+: GNU GPL version 3 or later
> > > <http://gnu.org/licenses/gpl.html>
> > > This is free software: you are free to change and redistribute it.
> > > There is NO WARRANTY, to the extent permitted by law.
> > > Type "show copying" and "show warranty" for details.
> > > This GDB was configured as "x86_64-portbld-freebsd12.2".
> > > Type "show configuration" for configuration details.
> > > For bug reporting instructions, please see:
> > > <https://www.gnu.org/software/gdb/bugs/>.
> > > Find the GDB manual and other documentation resources online at:
> > >      <http://www.gnu.org/software/gdb/documentation/>.
> > >
> > > For help, type "help".
> > > Type "apropos word" to search for commands related to "word"...
> > > Reading symbols from /boot/kernel/kernel...
> > > Reading symbols from /boot/kernel.LBLNET/kernel.debug...
> > >
> > > Unread portion of the kernel message buffer:
> > > Sleeping thread (tid 101408, pid 2046) owns a non-sleepable lock
> > > KDB: stack backtrace of thread 101408:
> > > sched_switch() at sched_switch+0x630/frame 0xfffffe0070e4f760
> > > mi_switch() at mi_switch+0xd4/frame 0xfffffe0070e4f790
> > > sleepq_catch_signals() at sleepq_catch_signals+0x403/frame
> > > 0xfffffe0070e4f7e0
> > > sleepq_timedwait_sig() at sleepq_timedwait_sig+0x14/frame
> > > 0xfffffe0070e4f820
> > > _sleep() at _sleep+0x1b3/frame 0xfffffe0070e4f8a0
> > > pps_ioctl() at pps_ioctl+0x298/frame 0xfffffe0070e4f8f0
> > > ppsioctl() at ppsioctl+0x48/frame 0xfffffe0070e4f920
> > > devfs_ioctl() at devfs_ioctl+0xb0/frame 0xfffffe0070e4f970
> > > VOP_IOCTL_APV() at VOP_IOCTL_APV+0x7b/frame 0xfffffe0070e4f9a0
> > > vn_ioctl() at vn_ioctl+0x16a/frame 0xfffffe0070e4fab0
> > > devfs_ioctl_f() at devfs_ioctl_f+0x1e/frame 0xfffffe0070e4fad0
> > > kern_ioctl() at kern_ioctl+0x2b7/frame 0xfffffe0070e4fb30
> > > sys_ioctl() at sys_ioctl+0xfa/frame 0xfffffe0070e4fc00
> > > amd64_syscall() at amd64_syscall+0x387/frame 0xfffffe0070e4fd30
> > > fast_syscall_common() at fast_syscall_common+0xf8/frame
> > > 0xfffffe0070e4fd30
> > > --- syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x8004c899a, rsp
> > > =
> > > 0x7fffdfdfc6a8, rbp = 0x7fffdfdfc730 ---
> > > panic: sleeping thread
> > > cpuid = 8
> > > time = 1630456142
> > > KDB: stack backtrace:
> > > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> > > 0xfffffe005ab73ab0
> > > vpanic() at vpanic+0x17b/frame 0xfffffe005ab73b00
> > > panic() at panic+0x43/frame 0xfffffe005ab73b60
> > > propagate_priority() at propagate_priority+0x282/frame
> > > 0xfffffe005ab73b90
> > > turnstile_wait() at turnstile_wait+0x30c/frame 0xfffffe005ab73be0
> > > __mtx_lock_sleep() at __mtx_lock_sleep+0x199/frame
> > > 0xfffffe005ab73c70
> > > ppcintr() at ppcintr+0x2a0/frame 0xfffffe005ab73c90
> > > ithread_loop() at ithread_loop+0x23c/frame 0xfffffe005ab73cf0
> > > fork_exit() at fork_exit+0x7e/frame 0xfffffe005ab73d30
> > > fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe005ab73d30
> > > --- trap 0, rip = 0, rsp = 0, rbp = 0 ---
> > > Uptime: 17m20s
> > > Dumping 607 out of 12240
> > > MB:..3%..11%..22%..32%..43%..51%..61%..72%..82%..93%
> > >
> > > __curthread () at /usr/src/sys/amd64/include/pcpu_aux.h:55
> > > 55      /usr/src/sys/amd64/include/pcpu_aux.h: No such file or
> > > directory.
> > > (kgdb) bt
> > > #0  __curthread () at /usr/src/sys/amd64/include/pcpu_aux.h:55
> > > #1  doadump (textdump=1) at ../../../kern/kern_shutdown.c:371
> > > #2  0xffffffff80b83ada in kern_reboot (howto=260)
> > >      at ../../../kern/kern_shutdown.c:451
> > > #3  0xffffffff80b83f33 in vpanic (fmt=<optimized out>,
> > > ap=<optimized out>)
> > >      at ../../../kern/kern_shutdown.c:880
> > > #4  0xffffffff80b83d53 in panic (fmt=<unavailable>)
> > >      at ../../../kern/kern_shutdown.c:807
> > > #5  0xffffffff80be7152 in propagate_priority
> > > (td=0xfffff80196959740)
> > >      at ../../../kern/subr_turnstile.c:228
> > > #6  0xffffffff80be7d1c in turnstile_wait (ts=0xfffff8000357a780,
> > >      owner=<optimized out>, queue=0) at
> > > ../../../kern/subr_turnstile.c:785
> > > #7  0xffffffff80b62ca9 in __mtx_lock_sleep (c=0xfffff80003969bd0,
> > >      v=<optimized out>) at ../../../kern/kern_mutex.c:654
> > > #8  0xffffffff8086fcc0 in ppcintr (arg=0xfffff80003969b00)
> > >      at ../../../dev/ppc/ppc.c:1546
> > > #9  0xffffffff80b4637c in intr_event_execute_handlers (p=<optimized
> > > out>,
> > >      ie=0xfffff800030d9d00) at ../../../kern/kern_intr.c:1143
> > > #10 ithread_execute_handlers (p=<optimized out>,
> > > ie=0xfffff800030d9d00)
> > >      at ../../../kern/kern_intr.c:1156
> > > #11 ithread_loop (arg=0xfffff800039aa7e0) at
> > > ../../../kern/kern_intr.c:1236
> > > #12 0xffffffff80b42e1e in fork_exit (
> > >      callout=0xffffffff80b46140 <ithread_loop>,
> > > arg=0xfffff800039aa7e0,
> > >      frame=0xfffffe005ab73d40) at ../../../kern/kern_fork.c:1080
> > > #13 <signal handler called>
> > > (kgdb)
> > >
>
>
>
Received on Wed Sep 01 2021 - 03:25:08 UTC

Original text of this message