Re: panic: mtx_lock_spin: recursed on non-recursive mutex uart_hwmtx...

On Mon, 2014-01-20 at 07:36 -0800, David Wolfskill wrote:
> I saw this on my "build machine" after updating the "head" slice from:
> 
> FreeBSD 11.0-CURRENT #1387  r260875M/260877:1100005: Sun Jan 19 11:57:25 PST 2014     root_at_freebeast.catwhisker.org:/common/S4/obj/usr/src/sys/GENERIC  i386
> 
> to
> 
> FreeBSD 11.0-CURRENT #1388  r260904M/260904:1100005: Mon Jan 20 06:25:53 PST 2014     root_at_freebeast.catwhisker.org:/common/S4/obj/usr/src/sys/GENERIC  i386
> 
> 
> A bit of context:  On this machine and my laptop, it is my practice to perform the following on a daily basis:
> * Ensure the machine is booted from slice 1 (stable/9).
> * Update the ports tree.
> * Update the source tree.
> * Start fetching any ports that are to be updated.
> * Update stable/9.
> * Reboot (staying on slice 1 -- stable/9).
> * Update the installed ports that warrant it ("portmaster -da --index").
> * Update the sources on slice 3 (stable/10).
> * Remove old libraries for stable/9 ("make delete-old-libs").
> * Reboot to slice 3 (stable/10).
> * Update stable/10.
> * Reboot (staying on slice 3 -- stable/10).
> * Update the sources on slice 4 (head).
> * Remove old libraries for stable/10 ("make delete-old-libs").
> * Reboot to slice 4 (head)
> * Update head.
> * Reboot (staying on slice 4 -- head).
> * Remove old libraries for head ("make delete-old-libs").
> 
> [If a given slice didn't have source updates, I don't try to rebuild
> FreeBSD on it, though.]
> 
> For my laptop, I then reboot to slice 1 (usually; sometimes slice
> 3, especially if there were no source updates for stable/9).  For
> the build machine, I set the default boot slice back to 1, then issue
> "shutdown -p now" to shut it off until just before midnight.
> 
> Today, there were a couple of perturbations from the above:
> * The only update for stable/10 I had was:
>   U    /S3/usr/src/release/doc/en_US.ISO8859-1/errata/article.xml
> 
>   so I decided that didn't warrant rebuilding FreeBSD stable/10.
> 
> * The panic in the Subject line -- only on the build machine.
> 
> Here's what I see (cut/paste) on serial console:
> 
> ...
> Jan 20 07:02:12 freebeast shutdown: power-down by david: 
> Stopping cron.
> Waiting for PIDS: 1090.
> Stopping sshd.
> Waiting for PIDS: 1080.
> Stopping rsyncd.
> Waiting for PIDS: 1057.
> Stopping powerd.
> Waiting for PIDS: 1042.
> sysctl: dev.cpu.0.freq=3600: Device not configured
> Stopping ntpd.
> Waiting for PIDS: 1039.
> Stopping lpd.
> Waiting for PIDS: 1018.
> Stopping lockd.
> Waiting for PIDS: 1001.
> Stopping statd.
> Waiting for PIDS: 998.
> Stopping nfsd.
> Waiting for PIDS: 994 995.
> Stopping mountd.
> Waiting for PIDS: 992.
> Stopping casperd.
> Waiting for PIDS: 951.
> Stopping amd.
> Waiting for PIDS: 943.
> Stopping ypbind.
> Stopping rpcbind.
> Waiting for PIDS: 916, 916.
> Stopping devd.
> Writing entropy file:.
> Terminated
> .
> Jan 20 07:02:16 freebeast syslogd: exiting on signal 15
> Waiting (max 60 seconds) for system process `vnlru' to stop...done
> Waiting (max 60 seconds) for system process `syncer' to stop...
> Syncing disks, vnodes remaining...2 4 4 4 3 3 3 2 1 1 0 0 0 0 done
> Waiting (max 60 seconds) for system process `bufdaemon' to stop...done
> All buffers synced.
> lock order reversal:
>  1st 0xc7336c68 ufs (ufs) _at_ /usr/src/sys/kern/vfs_mount.c:1237
>  2nd 0xc76846dc devfs (devfs) _at_ /usr/src/sys/ufs/ffs/ffs_vfsops.c:1412
> KDB: stack backtrace:
> db_trace_self_wrapper(c112d57c,a3231,e1fb9888,c0b1bfe7,1,...) at db_trace_self_wrapper+0x2d/frame 0xe1fb9828
> kdb_backtrace(c1131131,c76846dc,c1124024,c6dad2d0,c1162dc1,...) at kdb_backtrace+0x30/frame 0xe1fb9890
> witness_checkorder(c76846dc,9,c1162dc1,584,0,...) at witness_checkorder+0xc8a/frame 0xe1fb98e0
> __lockmgr_args(c76846dc,80400,c76846fc,0,0,0,c1162dc1,584) at __lockmgr_args+0x844/frame 0xe1fb99b4
> vop_stdlock(e1fb9a28,c6dad3a0,c6dad408,c169bc38,e1fb9a4c,...) at vop_stdlock+0x4d/frame 0xe1fb99e4
> VOP_LOCK1_APV(c13828dc,e1fb9a28,0,0,c13cded0,...) at VOP_LOCK1_APV+0x104/frame 0xe1fb9a10
> _vn_lock(c76846a8,80400,c1162dc1,584,c1393aac,...) at _vn_lock+0xa1/frame 0xe1fb9a50
> ffs_flushfiles(c753f000,a,c6f0a310,e1fb9b38,c0d416e3,...) at ffs_flushfiles+0x14c/frame 0xe1fb9a9c
> softdep_flushfiles(c753f000,2,c6f0a310,0,0,...) at softdep_flushfiles+0x6e/frame 0xe1fb9af0
> ffs_unmount(c753f000,80000,e1fb9b70,518,c6f0a310,...) at ffs_unmount+0x194/frame 0xe1fb9b38
> dounmount(c753f000,80000,c6f0a310,0,e1db3eb0,...) at dounmount+0x4dc/frame 0xe1fb9b98
> vfs_unmountall(e1db4058,0,c112895a,144,c6d8b1a0,...) at vfs_unmountall+0x4e/frame 0xe1fb9bb8
> kern_reboot(4008,0,c112895a,c3,0,...) at kern_reboot+0x5af/frame 0xe1fb9c20
> sys_reboot(c6f0a310,e1fb9cc8,14,c112b5b7,7a2,...) at sys_reboot+0x6f/frame 0xe1fb9c40
> syscall(e1fb9d08) at syscall+0x2de/frame 0xe1fb9cfc
> Xint0x80_syscall() at Xint0x80_syscall+0x21/frame 0xe1fb9cfc
> --- syscall (55, FreeBSD ELF32, sys_reboot), eip = 0x805a9df, esp = 0xbfbfd88c, ebp = 0xbfbfd960 ---
> Uptime: 4m28s
> panic: mtx_lock_spin: recursed on non-recursive mutex uart_hwmtx _at_ /usr/src/sys/dev/uart/uart_cpu.h:94
> 
> cpuid = 0
> KDB: stack backtrace:
> db_trace_self_wrapper(c112d57c,2f727375,2f637273,2f737973,2f766564,...) at db_trace_self_wrapper+0x2d/frame 0xe1fb9a60
> kdb_backtrace(c12ec1f3,0,c11269a2,e1fb9b38,e1fb9b08,...) at kdb_backtrace+0x30/frame 0xe1fb9ac8
> vpanic(c140d0c8,100,c11269a2,e1fb9b38,e1fb9b38,...) at vpanic+0x11f/frame 0xe1fb9b08
> kassert_panic(c11269a2,c10f66d8,c10f6758,5e,8,...) at kassert_panic+0xea/frame 0xe1fb9b2c
> __mtx_lock_spin_flags(c7291830,0,c10f6758,5e,c137d684,...) at __mtx_lock_spin_flags+0x190/frame 0xe1fb9b5c
> ns8250_bus_grab(c7291800,c7062b28,c137d684,5e,c140b9a4,...) at ns8250_bus_grab+0x40/frame 0xe1fb9b78
> uart_grab(c13fd070) at uart_grab+0x83/frame 0xe1fb9b9c
> uart_cngrab(c137d69c,88888889,e1fb9c20,c0ac7d43,c1128e43,...) at uart_cngrab+0x12/frame 0xe1fb9ba8
> cngrab(c1128e43,1c,c112895a,144,c6d8b1a0,...) at cngrab+0x33/frame 0xe1fb9bb8
> kern_reboot(4008,0,c112895a,c3,0,...) at kern_reboot+0x6d3/frame 0xe1fb9c20
> sys_reboot(c6f0a310,e1fb9cc8,14,c112b5b7,7a2,...) at sys_reboot+0x6f/frame 0xe1fb9c40
> syscall(e1fb9d08) at syscall+0x2de/frame 0xe1fb9cfc
> Xint0x80_syscall() at Xint0x80_syscall+0x21/frame 0xe1fb9cfc
> --- syscall (55, FreeBSD ELF32, sys_reboot), eip = 0x805a9df, esp = 0xbfbfd88c, ebp = 0xbfbfd960 ---
> KDB: enter: panic
> [ thread pid 1 tid 100002 ]
> Stopped at      kdb_enter+0x3d: movl    $0,kdb_why
> db> show locks
> exclusive sleep mutex Giant (Giant) r = 0 (0xc1724910) locked _at_ /usr/src/sys/vm/swap_pager.c:2365
> db> 
> 
> 
> When I issued "reset", the machine came back up normally (in slice
> 1 -- stable/9).  I then rebooted to slice 4 (head), and issued the
> same commands I usually do to set the default boot slice back to 1, then
> "shutdown -p now" -- and re-created the panic.
> 
> I can leave the machine up for a while if anyone has suggestions for me
> to poke around.  I have a local private mirror of the FreeBSD SVN repos
> and a spare bootable slice; I'm williing to try patches.  The machine
> isn't especially fast, but it's generally OK.
> 
> If it would be worthwhile, I could reboot my laptop to slice 4 (head) &
> attempt the same reset-to-slice-1-default & power-off.
> 
> This definitely did not happen _at_r260875, and it appears to be quite
> repeatable _at_r260904.
> 
> Peace,
> david

Since you mention serial console, I think r260890 might be a candidate.

-- Ian