kern/62216: perl syswrite not writing the buffer under (heavy) disk load

[Henri Hennebert]

>Number:         62216
>Category:       kern
>Synopsis:       perl syswrite not writing the buffer under (heavy) disk load
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Feb 01 05:20:19 PST 2004
>Closed-Date:
>Last-Modified:
>Originator:     Henri Hennebert
>Release:        FreeBSD 5.2-RELEASE i386
>Organization:
CIGER sa
>Environment:
System: FreeBSD norquay.cocoon.bel 5.2-RELEASE FreeBSD 5.2-RELEASE #0: Sun Jan 11 15:03:32 CET 2004 hlh at norquay.cocoon.bel:/usr/obj/usr/src/sys/NORQUAY i386

Summary of my perl5 (revision 5.0 version 8 subversion 2) configuration:
  Platform:
    osname=freebsd, osvers=5.2-rc, archname=i386-freebsd
    uname='freebsd norquay.cocoon.bel 5.2-rc freebsd 5.2-rc #0: thu dec 11 08:00:25 cet 2003 hlh at norquay.cocoon.bel:usrobjusrsrcsysnorquay i386 '
    config_args='-sde -Dprefix=/usr/local -Darchlib=/usr/local/lib/perl5/5.8.2/mach -Dprivlib=/usr/local/lib/perl5/5.8.2 -Dman3dir=/usr/local/lib/perl5/5.8.2/man/man3 -Dman1dir=/usr/local/man/man1 -Dsitearch=/usr/local/lib/perl5/site_perl/5.8.2/mach -Dsitelib=/usr/local/lib/perl5/site_perl/5.8.2 -Dscriptdir=/usr/local/bin -Ui_malloc -Ui_iconv -Uinstallusrbinperl -Dcc=cc -Doptimize=-O -pipe -march=pentium3 -Duseshrplib -Dccflags=-DAPPLLIB_EXP="/usr/local/lib/perl5/5.8.2/BSDPAN" -Ud_dosuid -Ui_gdbm -Dusethreads=n -Dusemymalloc=y'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=y, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-DAPPLLIB_EXP="/usr/local/lib/perl5/5.8.2/BSDPAN" -DHAS_FPSETMASK -DHAS_FLOATINGPOINT_H -fno-strict-aliasing -I/usr/local/include',
    optimize='-O -pipe -march=pentium3',
    cppflags='-DAPPLLIB_EXP="/usr/local/lib/perl5/5.8.2/BSDPAN" -DHAS_FPSETMASK -DHAS_FLOATINGPOINT_H -fno-strict-aliasing -I/usr/local/include'
    ccversion='', gccversion='3.3.3 [FreeBSD] 20031106', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags ='-Wl,-E  -L/usr/local/lib'
    libpth=/usr/lib /usr/local/lib
    libs=-lbind -lgdbm -lm -lcrypt -lutil -lc
    perllibs=-lbind -lm -lcrypt -lutil -lc
    libc=, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='  -Wl,-R/usr/local/lib/perl5/5.8.2/mach/CORE'
    cccdlflags='-DPIC -fPIC', lddlflags='-shared  -L/usr/local/lib'


Characteristics of this binary (from libperl):
  Compile-time options: USE_LARGE_FILES
  Built under freebsd
  Compiled at Dec 20 2003 13:33:01
  @INC:
    /usr/local/lib/perl5/site_perl/5.8.2/mach
    /usr/local/lib/perl5/site_perl/5.8.2
    /usr/local/lib/perl5/site_perl
    /usr/local/lib/perl5/5.8.2/BSDPAN
    /usr/local/lib/perl5/5.8.2/mach
    /usr/local/lib/perl5/5.8.2
    .

>Description:
When I install p5-Mail-Spamassassin, {site-perl}/Mail/Spamassassin.pm
and modules in {site-perl}/Mail/Spamassassin/ are truncated to 16384 bytes!
strange isn't it :-o . 

After digging I trace the culprit in
/usr/local/lib/perl5/5.8.2/ExtUtils/Install.pm. 

In fuction run_filter, I add 2 lines of debugging:

sub run_filter {
    my ($cmd, $src, $dest) = @_;
    local(*CMD, *SRC);
    open(CMD, "|$cmd >$dest") || die "Cannot fork: $!";
    open(SRC, $src)           || die "Cannot open $src: $!";
    my $buf;
    my $sz = 1024;
    while (my $len = sysread(SRC, $buf, $sz)) {
        print STDERR "$len=";        //DEBUG - print length read
        my $len_w = syswrite(CMD, $buf, $len);
        print STDERR "$len_w ";      //DEBUG - print length written
    }
    close SRC;
    close CMD or die "Filter command '$cmd' failed for $src";
}

If I run make
(in /usr/ports/mail/p5-Mail-SpamAssassin/work/Mail-SpamAssassin-2.61)
on a quiet machine, all is running well. My trace give me something like:

1024=1024 1024=1024 ... 390=390

Without the 2 `print STDERR', the files are truncated if make is run in
the same quiet condition. So the print modify the experiment (some
quantum theory here).

If I run make (after `make clean' and `perl Makefile.PL') during
a large copy from disk to disk, the trace give me:

1024=1024 10240=1024 ... 1024=1024 1024= 1024= 1024= ... 390= 
                                        ^     ^     ^        ^  
I conclude that syswrite do nothing, and don't return 0 as expected in
this case (maybe undef)!

For the record, I encounter this same problem in 5.1 some time ago but
don't study the problem at the time.

I make some google and mailing list searches and can't find any trace of
this problem elsewhere??? Maybe I am in a fold of spacetime ?

Any light is welcome.

Henri

>How-To-Repeat:
 
 See above.

>Fix:



>Release-Note:
>Audit-Trail:
>Unformatted: