r247839: broken pipe - for top, sudo and ports

[Jan Beich]

Jilles Tjoelker <jilles at stack.nl> writes:

> On Thu, Mar 07, 2013 at 04:54:01AM -0100, Jan Beich wrote:
>
>> Jilles Tjoelker <jilles at stack.nl> writes:
>
>> > On Tue, Mar 05, 2013 at 08:59:09PM +0100, Hartmann, O. wrote:
>
>> >> A "truss top" reveals this, is this of help?
>
>> >> [...]
>> >> stat("/etc/nsswitch.conf",{ mode=-rw-r--r--
>> >> ,inode=162310,size=1007,blksize=32768 }) = 0 (0x0)
>> >> stat("/etc/nsswitch.conf",{ mode=-rw-r--r--
>> >> ,inode=162310,size=1007,blksize=32768 }) = 0 (0x0)
>> >> stat("/etc/nsswitch.conf",{ mode=-rw-r--r--
>> >> ,inode=162310,size=1007,blksize=32768 }) = 0 (0x0)
>> >> stat("/etc/nsswitch.conf",{ mode=-rw-r--r--
>> >> ,inode=162310,size=1007,blksize=32768 }) = 0 (0x0)
>> >> stat("/etc/nsswitch.conf",{ mode=-rw-r--r--
>> >> ,inode=162310,size=1007,blksize=32768 }) = 0 (0x0)
>> >> socket(PF_LOCAL,SOCK_STREAM,0)                   = 4 (0x4)
>> >> connect(4,{ AF_UNIX "/var/run/nscd" },15)        = 0 (0x0)
>> >> fcntl(4,F_SETFL,O_NONBLOCK)                      = 0 (0x0)
>> >> kqueue(0x80183b000,0x80122fc58,0x10,0x80062b308,0x80183b010,0x2)
>> >> = 5 (0x5)
>> >> kevent(5,{0x4,EVFILT_WRITE,EV_ADD,0,0x0,0x0},1,0x0,0,0x0) = 0 (0x0)
>> >> kqueue(0x5,0x7fffffffd2e0,0x1,0x0,0x0,0x0)       = 6 (0x6)
>> >> kevent(6,{0x4,EVFILT_READ,EV_ADD,0,0x0,0x0},1,0x0,0,0x0) = 0 (0x0)
>> >> kevent(5,{0x4,EVFILT_WRITE,EV_ADD,1,0x4,0x0},1,0x0,0,0x0) = 0 (0x0)
>> >> kevent(5,0x0,0,{0x4,EVFILT_WRITE,EV_EOF,0,0x2000,0x0},1,0x0) = 1 (0x1)
>> >> sendmsg(0x4,0x7fffffffd290,0x0,0x1,0x1,0x0)      ERR#32 'Broken pipe'
>> >> SIGNAL 13 (SIGPIPE)
>> >> process exit, rval = 0
>
>> > Apparently there is a bug that causes nscd to close the connection
>> > immediately but even then it is wrong that this terminates the calling
>> > program with SIGPIPE.
>
>> > The below patch prevents the SIGPIPE but cannot revive the connection to
>> > nscd. This may cause numeric UIDs in top or increase the load on the
>> > directory server. It is compile tested only.
>> [...]
>
>> The patch seems to fix the issue in a world after r247804. I don't see
>> numeric UIDs in top but without the patch top crashes with SIGPIPE a lot
>> less frequently than sudo or make install (in base/ports) for me.
>
>> In my case shutting down nscd helped, too. Compared to stock
>> nsswitch.conf I only have "cache" added.
>
> Can you find what causes nscd to close the connection quickly, such as
> using ktrace?

# single user mode
$ ktrace -p $(pgrep nscd); top -b; ktrace -c; kdump
    71 nscd     GIO   fd 5 wrote 0 bytes
       ""
    71 nscd     GIO   fd 5 read 32 bytes
       0x0000 0400 0000 0000 0000 ffff 1000 0000 0000 0100  |..................|
       0x0012 0000 0000 0000 0000 0000 0000 0000            |..............|

    71 nscd     RET   kevent 1
    71 nscd     CALL  accept(0x4,0,0)
    71 nscd     RET   accept 6
    71 nscd     CALL  getsockopt(0x6,0,0x1,0x7fffff9fce28,0x7fffff9fce24)
    71 nscd     RET   getsockopt 0
    71 nscd     CALL  kevent(0x5,0x7fffff9fcf00,0x2,0,0,0x7fffff9fcf50)
    71 nscd     GIO   fd 5 wrote 64 bytes
       0x0000 0600 0000 0000 0000 f9ff 1100 0000 0000 401f  |................ at .|
       0x0012 0000 401f 0000 40e6 4002 0800 0000 0600 0000  |.. at ...@. at .........|
       0x0024 0000 0000 ffff 1100 0100 0000 0400 0000 0000  |..................|
       0x0036 0000 40e6 4002 0800 0000                      |.. at .@.....|

    71 nscd     GIO   fd 5 read 0 bytes
       ""
    71 nscd     RET   kevent 0
    71 nscd     CALL  kevent(0x5,0x7fffff9fcec0,0x1,0,0,0x7fffff9fcee0)
    71 nscd     GIO   fd 5 wrote 32 bytes
       0x0000 0400 0000 0000 0000 ffff 1100 0000 0000 0000  |..................|
       0x0012 0000 0000 0000 0000 0000 0000 0000            |..............|

    71 nscd     GIO   fd 5 read 0 bytes
       ""
    71 nscd     RET   kevent 0
    71 nscd     CALL  kevent(0x5,0,0,0x7fffff9fcec0,0x1,0)
    71 nscd     GIO   fd 5 wrote 0 bytes
       ""
    71 nscd     GIO   fd 5 read 32 bytes
       0x0000 0600 0000 0000 0000 f9ff 3000 0000 0000 0100  |..........0.......|
       0x0012 0000 0000 0000 40e6 4002 0800 0000            |...... at .@.....|

    71 nscd     RET   kevent 1
    71 nscd     CALL  close(0x6)
    71 nscd     RET   close 0
    71 nscd     CALL  kevent(0x5,0,0,0x7fffff9fcec0,0x1,0)