Re: panic: Lock so_rcv_sx not exclusively locked

On Mon, 28 Jan 2008, Kip Macy wrote:

Thanks for the bug report. It looks like this can probably be fixed by simply not calling sbunlock if sblock failed. I anticipate this being fixed shortly.

It looks like the logic is in somewhat the wrong order in sorflush() -- likely we should be issuing socantrcvmore_locked() before sblock() in order to dislodge the threads currently using the socket/socket buffer, then perform a non-interruptible sblock() to wait for them to fall out. However, it would be useful to confirm what the other threads are doing--most likely blocked on read, but I want to be sure.

Robert N M Watson
Computer Laboratory
University of Cambridge


-Kip


On Jan 28, 2008 10:08 AM, Jos Backus <jos@xxxxxxxxxxx> wrote:
Recent -current kernels can reliably be made to panic by killing npviewer.bin.
Right before killing, npviewer.bin shows up like this in top:

6288 jos 1 45 5 62844K 36788K so_rcv 0:08 0.00% npviewer.bin

lizzy:~/crash% kgdb /usr/obj/usr/src/sys/LIZZY/kernel.debug vmcore.1
kgdb: kvm_nlist(_stopped_cpus):
kgdb: kvm_nlist(_stoppcbs):
[GDB will not be able to debug user-mode threads: /usr/lib/libthread_db.so: Undefined symbol "ps_pglobal_lookup"]
GNU gdb 6.1.1 [FreeBSD]
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GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
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This GDB was configured as "i386-marcel-freebsd".

Unread portion of the kernel message buffer:
panic: Lock so_rcv_sx not exclusively locked @ /usr/src/sys/kern/uipc_sockbuf.c:157

Uptime: 5h23m39s
Physical memory: 1527 MB
Dumping 247 MB: 232 216 200 184 168 152 136 120 104 88 72 56 40 24 8

#0 doadump () at pcpu.h:195
195 pcpu.h: No such file or directory.
in pcpu.h
(kgdb) bt
#0 doadump () at pcpu.h:195
#1 0xc05435ef in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:417
#2 0xc0543867 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:571
#3 0xc054a427 in _sx_assert (sx=0xc4fb89a0, what=4,
file=0xc06d49ca "/usr/src/sys/kern/uipc_sockbuf.c", line=157)
at /usr/src/sys/kern/kern_sx.c:931
#4 0xc054a8da in _sx_xunlock (sx=0xc4fb89a0,
file=0xc06d49ca "/usr/src/sys/kern/uipc_sockbuf.c", line=157)
at /usr/src/sys/kern/kern_sx.c:316
#5 0xc0595444 in sbunlock (sb=0xc4fb8968)
at /usr/src/sys/kern/uipc_sockbuf.c:157
#6 0xc0598245 in sorflush (so=0xc4fb8918)
at /usr/src/sys/kern/uipc_socket.c:1902
#7 0xc05982df in soshutdown (so=0xc4fb8918, how=2)
at /usr/src/sys/kern/uipc_socket.c:1866
#8 0xc059ce86 in shutdown (td=0xc4b31880, uap=0xe7219c58)
at /usr/src/sys/kern/uipc_syscalls.c:1248
#9 0xc07ffa80 in ?? ()
#10 0xc4b31880 in ?? ()
#11 0xe7219c58 in ?? ()
#12 0x00000008 in ?? ()
#13 0x00000000 in ?? ()
#14 0x00000000 in ?? ()
#15 0xc103d800 in ?? ()
#16 0x00000c1e in ?? ()
#17 0x00000000 in ?? ()
#18 0xc4e25488 in ?? ()
#19 0xc5007e9c in ?? ()
#20 0x00000000 in ?? ()
#21 0x00000000 in ?? ()
#22 0xe7219c72 in ?? ()
#23 0x00000004 in ?? ()
#24 0x80000000 in ?? ()
#25 0xe7219c8c in ?? ()
---Type <return> to continue, or q <return> to quit---
#26 0xc06a1a44 in __qdivrem (uq=Unhandled dwarf expression opcode 0x93
) at /usr/src/sys/libkern/qdivrem.c:186
#27 0xc0697b93 in syscall (frame=0xe7219d38)
at /usr/src/sys/i386/i386/trap.c:1034
#28 0xc06818b0 in Xint0x80_syscall () at /usr/src/sys/i386/i386/exception.s:203
#29 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb)


--
Jos Backus
jos at catnook.com
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