Revision 72853e2991a2702ae93aaf889ac7db743a415dd3 authored by Mel Gorman on 09 September 2010, 23:38:16 UTC, committed by Linus Torvalds on 10 September 2010, 01:57:25 UTC
When allocating a page, the system uses NR_FREE_PAGES counters to determine if watermarks would remain intact after the allocation was made. This check is made without interrupts disabled or the zone lock held and so is race-prone by nature. Unfortunately, when pages are being freed in batch, the counters are updated before the pages are added on the list. During this window, the counters are misleading as the pages do not exist yet. When under significant pressure on systems with large numbers of CPUs, it's possible for processes to make progress even though they should have been stalled. This is particularly problematic if a number of the processes are using GFP_ATOMIC as the min watermark can be accidentally breached and in extreme cases, the system can livelock. This patch updates the counters after the pages have been added to the list. This makes the allocator more cautious with respect to preserving the watermarks and mitigates livelock possibilities. [akpm@linux-foundation.org: avoid modifying incoming args] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: Christoph Lameter <cl@linux.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 5ee28a4
namespace.pl
#!/usr/bin/perl -w
#
# namespace.pl. Mon Aug 30 2004
#
# Perform a name space analysis on the linux kernel.
#
# Copyright Keith Owens <kaos@ocs.com.au>. GPL.
#
# Invoke by changing directory to the top of the kernel object
# tree then namespace.pl, no parameters.
#
# Tuned for 2.1.x kernels with the new module handling, it will
# work with 2.0 kernels as well.
#
# Last change 2.6.9-rc1, adding support for separate source and object
# trees.
#
# The source must be compiled/assembled first, the object files
# are the primary input to this script. Incomplete or missing
# objects will result in a flawed analysis. Compile both vmlinux
# and modules.
#
# Even with complete objects, treat the result of the analysis
# with caution. Some external references are only used by
# certain architectures, others with certain combinations of
# configuration parameters. Ideally the source should include
# something like
#
# #ifndef CONFIG_...
# static
# #endif
# symbol_definition;
#
# so the symbols are defined as static unless a particular
# CONFIG_... requires it to be external.
#
# A symbol that is suffixed with '(export only)' has these properties
#
# * It is global.
# * It is marked EXPORT_SYMBOL or EXPORT_SYMBOL_GPL, either in the same
# source file or a different source file.
# * Given the current .config, nothing uses the symbol.
#
# The symbol is a candidate for conversion to static, plus removal of the
# export. But be careful that a different .config might use the symbol.
#
#
# Name space analysis and cleanup is an iterative process. You cannot
# expect to find all the problems in a single pass.
#
# * Identify possibly unnecessary global declarations, verify that they
# really are unnecessary and change them to static.
# * Compile and fix up gcc warnings about static, removing dead symbols
# as necessary.
# * make clean and rebuild with different configs (especially
# CONFIG_MODULES=n) to see which symbols are being defined when the
# config does not require them. These symbols bloat the kernel object
# for no good reason, which is frustrating for embedded systems.
# * Wrap config sensitive symbols in #ifdef CONFIG_foo, as long as the
# code does not get too ugly.
# * Repeat the name space analysis until you can live with with the
# result.
#
require 5; # at least perl 5
use strict;
use File::Find;
my $nm = ($ENV{'NM'} || "nm") . " -p";
my $objdump = ($ENV{'OBJDUMP'} || "objdump") . " -s -j .comment";
my $srctree = "";
my $objtree = "";
$srctree = "$ENV{'srctree'}/" if (exists($ENV{'srctree'}));
$objtree = "$ENV{'objtree'}/" if (exists($ENV{'objtree'}));
if ($#ARGV != -1) {
print STDERR "usage: $0 takes no parameters\n";
die("giving up\n");
}
my %nmdata = (); # nm data for each object
my %def = (); # all definitions for each name
my %ksymtab = (); # names that appear in __ksymtab_
my %ref = (); # $ref{$name} exists if there is a true external reference to $name
my %export = (); # $export{$name} exists if there is an EXPORT_... of $name
&find(\&linux_objects, '.'); # find the objects and do_nm on them
&list_multiply_defined();
&resolve_external_references();
&list_extra_externals();
exit(0);
sub linux_objects
{
# Select objects, ignoring objects which are only created by
# merging other objects. Also ignore all of modules, scripts
# and compressed. Most conglomerate objects are handled by do_nm,
# this list only contains the special cases. These include objects
# that are linked from just one other object and objects for which
# there is really no permanent source file.
my $basename = $_;
$_ = $File::Find::name;
s:^\./::;
if (/.*\.o$/ &&
! (
m:/built-in.o$:
|| m:arch/x86/kernel/vsyscall-syms.o$:
|| m:arch/ia64/ia32/ia32.o$:
|| m:arch/ia64/kernel/gate-syms.o$:
|| m:arch/ia64/lib/__divdi3.o$:
|| m:arch/ia64/lib/__divsi3.o$:
|| m:arch/ia64/lib/__moddi3.o$:
|| m:arch/ia64/lib/__modsi3.o$:
|| m:arch/ia64/lib/__udivdi3.o$:
|| m:arch/ia64/lib/__udivsi3.o$:
|| m:arch/ia64/lib/__umoddi3.o$:
|| m:arch/ia64/lib/__umodsi3.o$:
|| m:arch/ia64/scripts/check_gas_for_hint.o$:
|| m:arch/ia64/sn/kernel/xp.o$:
|| m:boot/bbootsect.o$:
|| m:boot/bsetup.o$:
|| m:/bootsect.o$:
|| m:/boot/setup.o$:
|| m:/compressed/:
|| m:drivers/cdrom/driver.o$:
|| m:drivers/char/drm/tdfx_drv.o$:
|| m:drivers/ide/ide-detect.o$:
|| m:drivers/ide/pci/idedriver-pci.o$:
|| m:drivers/media/media.o$:
|| m:drivers/scsi/sd_mod.o$:
|| m:drivers/video/video.o$:
|| m:fs/devpts/devpts.o$:
|| m:fs/exportfs/exportfs.o$:
|| m:fs/hugetlbfs/hugetlbfs.o$:
|| m:fs/msdos/msdos.o$:
|| m:fs/nls/nls.o$:
|| m:fs/ramfs/ramfs.o$:
|| m:fs/romfs/romfs.o$:
|| m:fs/vfat/vfat.o$:
|| m:init/mounts.o$:
|| m:^modules/:
|| m:net/netlink/netlink.o$:
|| m:net/sched/sched.o$:
|| m:/piggy.o$:
|| m:^scripts/:
|| m:sound/.*/snd-:
|| m:^.*/\.tmp_:
|| m:^\.tmp_:
|| m:/vmlinux-obj.o$:
)
) {
do_nm($basename, $_);
}
$_ = $basename; # File::Find expects $_ untouched (undocumented)
}
sub do_nm
{
my ($basename, $fullname) = @_;
my ($source, $type, $name);
if (! -e $basename) {
printf STDERR "$basename does not exist\n";
return;
}
if ($fullname !~ /\.o$/) {
printf STDERR "$fullname is not an object file\n";
return;
}
($source = $fullname) =~ s/\.o$//;
if (-e "$objtree$source.c" || -e "$objtree$source.S") {
$source = "$objtree$source";
} else {
$source = "$srctree$source";
}
if (! -e "$source.c" && ! -e "$source.S") {
# No obvious source, exclude the object if it is conglomerate
open(my $objdumpdata, "$objdump $basename|")
or die "$objdump $fullname failed $!\n";
my $comment;
while (<$objdumpdata>) {
chomp();
if (/^In archive/) {
# Archives are always conglomerate
$comment = "GCC:GCC:";
last;
}
next if (! /^[ 0-9a-f]{5,} /);
$comment .= substr($_, 43);
}
close($objdumpdata);
if (!defined($comment) || $comment !~ /GCC\:.*GCC\:/m) {
printf STDERR "No source file found for $fullname\n";
}
return;
}
open (my $nmdata, "$nm $basename|")
or die "$nm $fullname failed $!\n";
my @nmdata;
while (<$nmdata>) {
chop;
($type, $name) = (split(/ +/, $_, 3))[1..2];
# Expected types
# A absolute symbol
# B weak external reference to data that has been resolved
# C global variable, uninitialised
# D global variable, initialised
# G global variable, initialised, small data section
# R global array, initialised
# S global variable, uninitialised, small bss
# T global label/procedure
# U external reference
# W weak external reference to text that has been resolved
# a assembler equate
# b static variable, uninitialised
# d static variable, initialised
# g static variable, initialised, small data section
# r static array, initialised
# s static variable, uninitialised, small bss
# t static label/procedures
# w weak external reference to text that has not been resolved
# ? undefined type, used a lot by modules
if ($type !~ /^[ABCDGRSTUWabdgrstw?]$/) {
printf STDERR "nm output for $fullname contains unknown type '$_'\n";
}
elsif ($name =~ /\./) {
# name with '.' is local static
}
else {
$type = 'R' if ($type eq '?'); # binutils replaced ? with R at one point
# binutils keeps changing the type for exported symbols, force it to R
$type = 'R' if ($name =~ /^__ksymtab/ || $name =~ /^__kstrtab/);
$name =~ s/_R[a-f0-9]{8}$//; # module versions adds this
if ($type =~ /[ABCDGRSTW]/ &&
$name ne 'init_module' &&
$name ne 'cleanup_module' &&
$name ne 'Using_Versions' &&
$name !~ /^Version_[0-9]+$/ &&
$name !~ /^__parm_/ &&
$name !~ /^__kstrtab/ &&
$name !~ /^__ksymtab/ &&
$name !~ /^__kcrctab_/ &&
$name !~ /^__exitcall_/ &&
$name !~ /^__initcall_/ &&
$name !~ /^__kdb_initcall_/ &&
$name !~ /^__kdb_exitcall_/ &&
$name !~ /^__module_/ &&
$name !~ /^__mod_/ &&
$name !~ /^__crc_/ &&
$name ne '__this_module' &&
$name ne 'kernel_version') {
if (!exists($def{$name})) {
$def{$name} = [];
}
push(@{$def{$name}}, $fullname);
}
push(@nmdata, "$type $name");
if ($name =~ /^__ksymtab_/) {
$name = substr($name, 10);
if (!exists($ksymtab{$name})) {
$ksymtab{$name} = [];
}
push(@{$ksymtab{$name}}, $fullname);
}
}
}
close($nmdata);
if ($#nmdata < 0) {
if (
$fullname ne "lib/brlock.o"
&& $fullname ne "lib/dec_and_lock.o"
&& $fullname ne "fs/xfs/xfs_macros.o"
&& $fullname ne "drivers/ide/ide-probe-mini.o"
&& $fullname ne "usr/initramfs_data.o"
&& $fullname ne "drivers/acpi/executer/exdump.o"
&& $fullname ne "drivers/acpi/resources/rsdump.o"
&& $fullname ne "drivers/acpi/namespace/nsdumpdv.o"
&& $fullname ne "drivers/acpi/namespace/nsdump.o"
&& $fullname ne "arch/ia64/sn/kernel/sn2/io.o"
&& $fullname ne "arch/ia64/kernel/gate-data.o"
&& $fullname ne "drivers/ieee1394/oui.o"
&& $fullname ne "security/capability.o"
&& $fullname ne "sound/core/wrappers.o"
&& $fullname ne "fs/ntfs/sysctl.o"
&& $fullname ne "fs/jfs/jfs_debug.o"
) {
printf "No nm data for $fullname\n";
}
return;
}
$nmdata{$fullname} = \@nmdata;
}
sub drop_def
{
my ($object, $name) = @_;
my $nmdata = $nmdata{$object};
my ($i, $j);
for ($i = 0; $i <= $#{$nmdata}; ++$i) {
if ($name eq (split(' ', $nmdata->[$i], 2))[1]) {
splice(@{$nmdata{$object}}, $i, 1);
my $def = $def{$name};
for ($j = 0; $j < $#{$def{$name}}; ++$j) {
if ($def{$name}[$j] eq $object) {
splice(@{$def{$name}}, $j, 1);
}
}
last;
}
}
}
sub list_multiply_defined
{
foreach my $name (keys(%def)) {
if ($#{$def{$name}} > 0) {
# Special case for cond_syscall
if ($#{$def{$name}} == 1 && $name =~ /^sys_/ &&
($def{$name}[0] eq "kernel/sys.o" ||
$def{$name}[1] eq "kernel/sys.o")) {
&drop_def("kernel/sys.o", $name);
next;
}
# Special case for i386 entry code
if ($#{$def{$name}} == 1 && $name =~ /^__kernel_/ &&
$def{$name}[0] eq "arch/x86/kernel/vsyscall-int80_32.o" &&
$def{$name}[1] eq "arch/x86/kernel/vsyscall-sysenter_32.o") {
&drop_def("arch/x86/kernel/vsyscall-sysenter_32.o", $name);
next;
}
printf "$name is multiply defined in :-\n";
foreach my $module (@{$def{$name}}) {
printf "\t$module\n";
}
}
}
}
sub resolve_external_references
{
my ($kstrtab, $ksymtab, $export);
printf "\n";
foreach my $object (keys(%nmdata)) {
my $nmdata = $nmdata{$object};
for (my $i = 0; $i <= $#{$nmdata}; ++$i) {
my ($type, $name) = split(' ', $nmdata->[$i], 2);
if ($type eq "U" || $type eq "w") {
if (exists($def{$name}) || exists($ksymtab{$name})) {
# add the owning object to the nmdata
$nmdata->[$i] = "$type $name $object";
# only count as a reference if it is not EXPORT_...
$kstrtab = "R __kstrtab_$name";
$ksymtab = "R __ksymtab_$name";
$export = 0;
for (my $j = 0; $j <= $#{$nmdata}; ++$j) {
if ($nmdata->[$j] eq $kstrtab ||
$nmdata->[$j] eq $ksymtab) {
$export = 1;
last;
}
}
if ($export) {
$export{$name} = "";
}
else {
$ref{$name} = ""
}
}
elsif ( $name ne "mod_use_count_"
&& $name ne "__initramfs_end"
&& $name ne "__initramfs_start"
&& $name ne "_einittext"
&& $name ne "_sinittext"
&& $name ne "kallsyms_names"
&& $name ne "kallsyms_num_syms"
&& $name ne "kallsyms_addresses"
&& $name ne "__this_module"
&& $name ne "_etext"
&& $name ne "_edata"
&& $name ne "_end"
&& $name ne "__bss_start"
&& $name ne "_text"
&& $name ne "_stext"
&& $name ne "__gp"
&& $name ne "ia64_unw_start"
&& $name ne "ia64_unw_end"
&& $name ne "__init_begin"
&& $name ne "__init_end"
&& $name ne "__bss_stop"
&& $name ne "__nosave_begin"
&& $name ne "__nosave_end"
&& $name ne "pg0"
&& $name ne "__module_text_address"
&& $name !~ /^__sched_text_/
&& $name !~ /^__start_/
&& $name !~ /^__end_/
&& $name !~ /^__stop_/
&& $name !~ /^__scheduling_functions_.*_here/
&& $name !~ /^__.*initcall_/
&& $name !~ /^__.*per_cpu_start/
&& $name !~ /^__.*per_cpu_end/
&& $name !~ /^__alt_instructions/
&& $name !~ /^__setup_/
&& $name !~ /^jiffies/
&& $name !~ /^__mod_timer/
&& $name !~ /^__mod_page_state/
&& $name !~ /^init_module/
&& $name !~ /^cleanup_module/
) {
printf "Cannot resolve ";
printf "weak " if ($type eq "w");
printf "reference to $name from $object\n";
}
}
}
}
}
sub list_extra_externals
{
my %noref = ();
foreach my $name (keys(%def)) {
if (! exists($ref{$name})) {
my @module = @{$def{$name}};
foreach my $module (@module) {
if (! exists($noref{$module})) {
$noref{$module} = [];
}
push(@{$noref{$module}}, $name);
}
}
}
if (%noref) {
printf "\nExternally defined symbols with no external references\n";
foreach my $module (sort(keys(%noref))) {
printf " $module\n";
foreach (sort(@{$noref{$module}})) {
my $export;
if (exists($export{$_})) {
$export = " (export only)";
} else {
$export = "";
}
printf " $_$export\n";
}
}
}
}
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