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Date:      Mon, 26 Oct 2009 09:05:48 -0500
From:      Jaime Bozza <jbozza@mindsites.com>
To:        Dylan Cochran <heliocentric@gmail.com>
Cc:        "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org>
Subject:   RE: Possible scheduler (SCHED_ULE) bug?
Message-ID:  <CF092998EA82AE4D83AF9C9ECA9A8BDE02EB411A94@ATLAS.msg.local>
In-Reply-To: <bdf82f800910231328tfa4decfncd70ae0daad2bef6@mail.gmail.com>
References:  <CF092998EA82AE4D83AF9C9ECA9A8BDE02EB411A85@ATLAS.msg.local> <bdf82f800910231328tfa4decfncd70ae0daad2bef6@mail.gmail.com>

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Sincerely,

Jaime Bozza
MindSites Group, LLC


From: Dylan Cochran [mailto:heliocentric@gmail.com]
> Superficially, this seams identical to a deadlock I reported for
> 7.1-RC1. Would you mind compiling a kernel with these options:
>=20
> <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 =3D 0xc07ff29d, esp =3D 0xe66e0b48, ebp =3D 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 =3D 0x282cb0cb, esp =3D
> 0xbfbfc7cc, ebp =3D 0xbfbfe848 ---
> KDB: enter: watchdog timeout
>=20
> 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. =20
kern_sendfile+0x6ad
do_sendfile+0xb1
sendfile+0x13

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

(kgdb) backtrace
#0  doadump () at pcpu.h:196
#1  0xc07f2c57 in boot (howto=3D260) at /usr/src/sys/kern/kern_shutdown.c:4=
18
#2  0xc07f2f62 in panic (fmt=3DVariable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:574
#3  0xc0497e47 in db_panic (addr=3DCould not find the frame base for "db_pa=
nic".
) at /usr/src/sys/ddb/db_command.c:446
#4  0xc04985bc in db_command (last_cmdp=3D0xc0ca9154, cmd_table=3D0x0, dopa=
ger=3D1) 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=3D3, code=3D0) at /usr/src/sys/ddb/db_main.=
c:228
#7  0xc081fdf6 in kdb_trap (type=3D3, code=3D0, tf=3D0xc72e2a5c) at /usr/sr=
c/sys/kern/subr_kdb.c:524
#8  0xc0b01b9b in trap (frame=3D0xc72e2a5c) 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=3D0xc0b677b2 "watchdog", msg=3D0xc0b7e=
f1d "watchdog timeout") at cpufunc.h:60
#11 0xc07b0cad in hardclock (usermode=3D0, pc=3D3229966301) at /usr/src/sys=
/kern/kern_clock.c:640
#12 0xc0aedf1c in lapic_handle_timer (frame=3D0xc72e2afc) at /usr/src/sys/i=
386/i386/local_apic.c:785
#13 0xc0ae5edf in Xtimerint () at apic_vector.s:108
#14 0xc0855fdd in kern_sendfile (td=3D0xc771db40, uap=3D0xc72e2cfc, hdr_uio=
=3D0x0, trl_uio=3D0x0, compat=3D0) at atomic.h:160
#15 0xc0856d31 in do_sendfile (td=3D0xc771db40, uap=3D0xc72e2cfc, compat=3D=
0) at /usr/src/sys/kern/uipc_syscalls.c:1775
#16 0xc0856dd3 in sendfile (td=3D0xc771db40, uap=3D0xc72e2cfc) at /usr/src/=
sys/kern/uipc_syscalls.c:1746
#17 0xc0b01365 in syscall (frame=3D0xc72e2d38) at /usr/src/sys/i386/i386/tr=
ap.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 an=
ything else!

Jaime




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