Re: ftpd problems (probably kernel's fault)

["Julio M. Merino Vidal" <jmmv84%gmail.com@localhost>]

On Tue, Apr 29, 2008 at 3:17 PM, Andrew Doran <ad%netbsd.org@localhost> wrote:
>
> On Tue, Apr 29, 2008 at 02:46:03PM +0200, Julio M. Merino Vidal wrote:
>  >
>  > With your change, the message:
>  >
>  >     ftp: Can't send abort message: No buffer space available
>  >
>  > is gone, but connections to the local ftpd still get stalled.
>
>  Can you see what ftpd is stalled on? Could you please get a backtrace from
>  it, and any other threads hanging in tstile or anything else that is
>  interesting?
>
>  You can get a kernel backtrace using ddb, or gdb. For gdb run the following
>
>         ps -axs -o pid,lid,wchan,laddr,comm | grep -i whatever

portal:~> ps -axs -o pid,lid,wchan,laddr,comm | grep -i ftpd
17278    1 netio    ffff80004b661420 ftpd: localhost: anonymous/: RETR
atf-cam0.mpg
portal:~>

>  Pick an interesting value of laddr.. Then
>
>  gdb /mykernel
>  target kvm /dev/mem
>  kvm proc $laddr
>  bt

Wow, that's neat.  Here is it:

#0  0xffffffff802cc21d in mi_switch (l=0xffff80004b661420) at
/usr/src/sys/kern/kern_synch.c:827
#1  0xffffffff802c7f6a in sleepq_block (timo=0, catch=true) at
/usr/src/sys/kern/kern_sleepq.c:263
#2  0xffffffff802a69a9 in cv_timedwait_sig (cv=0xffff8000045fe0f0,
mtx=0xffff8000479e6f80, timo=0) at
/usr/src/sys/kern/kern_condvar.c:259
#3  0xffffffff80317b52 in sbwait (sb=0xffff8000045fe0b0) at
/usr/src/sys/kern/uipc_socket2.c:414
#4  0xffffffff80314742 in sosend (so=0xffff8000045fe020, addr=0x0,
uio=0xffff80004af6db90, top=0x0, control=0x0, flags=<value optimized
out>,
    l=0xffff80004b661420) at /usr/src/sys/kern/uipc_socket.c:897
#5  0xffffffff802fdacd in soo_write (fp=<value optimized out>,
offset=<value optimized out>, uio=0x0, cred=<value optimized out>,
    flags=<value optimized out>) at /usr/src/sys/kern/sys_socket.c:107
#6  0xffffffff802f2eae in dofilewrite (fd=8, fp=0x0,
buf=0x7f7ffd439000, nbyte=16384, offset=0x0, flags=0,
retval=0xffff80004af6dc30)
    at /usr/src/sys/kern/sys_generic.c:355
#7  0xffffffff802f2fe2 in sys_write (l=<value optimized out>,
uap=0xffff80004af6dc80, retval=0xffff80004af6dc30)
    at /usr/src/sys/kern/sys_generic.c:323
#8  0xffffffff80373f3a in syscall (frame=0xffff80004af6dc80) at
/usr/src/sys/arch/amd64/amd64/syscall.c:123
#9  0xffffffff801005e8 in Xsyscall ()

Thanks.

-- 
Julio M. Merino Vidal <jmmv84%gmail.com@localhost>