Possible scheduler (SCHED_ULE) bug?

[Jaime Bozza]

Sincerely,

Jaime Bozza
MindSites Group, LLC


From: Dylan Cochran [mailto:heliocentric at gmail.com]
> Superficially, this seams identical to a deadlock I reported for
> 7.1-RC1. Would you mind compiling a kernel with these options:
> 
> <snip>
> KDB: stack backtrace:
> db_trace_self_wrapper(c0b55b52,e66e0ae0,c07615e9,c0b50617,8ca93,...)
> at db_trace_self_wrapper+0x26
> kdb_backtrace(c0b50617,8ca93,0,c41a7690,2,...) at kdb_backtrace+0x29
> hardclock(0,c07ff29d,0,0,4,...) at hardclock+0x1f9
> lapic_handle_timer(e66e0b08) at lapic_handle_timer+0x9c
> Xtimerint() at Xtimerint+0x1f
> --- interrupt, eip = 0xc07ff29d, esp = 0xe66e0b48, ebp = 0xe66e0c34 ---
> kern_sendfile(c41a7690,e66e0cfc,0,0,0,...) at kern_sendfile+0x90d
> do_sendfile(e66e0d2c,c0aba265,c41a7690,e66e0cfc,20,...) at
> do_sendfile+0xb1
> sendfile(c41a7690,e66e0cfc,20,16,e66e0d2c,...) at sendfile+0x13
> syscall(e66e0d38) at syscall+0x335
> Xint0x80_syscall() at Xint0x80_syscall+0x20
> --- syscall (393, FreeBSD ELF32, sendfile), eip = 0x282cb0cb, esp =
> 0xbfbfc7cc, ebp = 0xbfbfe848 ---
> KDB: enter: watchdog timeout
> 
> You can type 'reboot' to reboot the machine (in my case, panic would
> not work, so a useful dump wasn't in the cards)

Different offset on mine, but of course I'm using a different kernel.  
kern_sendfile+0x6ad
do_sendfile+0xb1
sendfile+0x13

Luckily, I was able to get a panic, so I have all the files necessary to debug.  Here's the backtrace:

(kgdb) backtrace
#0  doadump () at pcpu.h:196
#1  0xc07f2c57 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:418
#2  0xc07f2f62 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:574
#3  0xc0497e47 in db_panic (addr=Could not find the frame base for "db_panic".
) at /usr/src/sys/ddb/db_command.c:446
#4  0xc04985bc in db_command (last_cmdp=0xc0ca9154, cmd_table=0x0, dopager=1) at /usr/src/sys/ddb/db_command.c:413
#5  0xc04986ca in db_command_loop () at /usr/src/sys/ddb/db_command.c:466
#6  0xc049a17d in db_trap (type=3, code=0) at /usr/src/sys/ddb/db_main.c:228
#7  0xc081fdf6 in kdb_trap (type=3, code=0, tf=0xc72e2a5c) at /usr/src/sys/kern/subr_kdb.c:524
#8  0xc0b01b9b in trap (frame=0xc72e2a5c) at /usr/src/sys/i386/i386/trap.c:692
#9  0xc0ae58fb in calltrap () at /usr/src/sys/i386/i386/exception.s:166
#10 0xc081ff7a in kdb_enter_why (why=0xc0b677b2 "watchdog", msg=0xc0b7ef1d "watchdog timeout") at cpufunc.h:60
#11 0xc07b0cad in hardclock (usermode=0, pc=3229966301) at /usr/src/sys/kern/kern_clock.c:640
#12 0xc0aedf1c in lapic_handle_timer (frame=0xc72e2afc) at /usr/src/sys/i386/i386/local_apic.c:785
#13 0xc0ae5edf in Xtimerint () at apic_vector.s:108
#14 0xc0855fdd in kern_sendfile (td=0xc771db40, uap=0xc72e2cfc, hdr_uio=0x0, trl_uio=0x0, compat=0) at atomic.h:160
#15 0xc0856d31 in do_sendfile (td=0xc771db40, uap=0xc72e2cfc, compat=0) at /usr/src/sys/kern/uipc_syscalls.c:1775
#16 0xc0856dd3 in sendfile (td=0xc771db40, uap=0xc72e2cfc) at /usr/src/sys/kern/uipc_syscalls.c:1746
#17 0xc0b01365 in syscall (frame=0xc72e2d38) at /usr/src/sys/i386/i386/trap.c:1094
#18 0xc0ae5960 in Xint0x80_syscall () at /usr/src/sys/i386/i386/exception.s:262
#19 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)

This is all a bit new to me (debugging, etc), so let me know if you need anything else!

Jaime