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Subjecthlist_for_each_entry && pos (Was: task_work_queue)
On 04/12, Oleg Nesterov wrote:
>
> + hlist_for_each_entry(twork, pos, &task->task_works, hlist) {

This reminds me.

hlist_for_each_entry_*() do not need "pos", it can be

#define hlist_for_each_entry(pos, head, member) \
for (pos = (void*)(head)->first; \
pos && ({ pos = hlist_entry((void*)pos, typeof(*pos), member); 1; }); \
pos = (void*)(pos)->member.next)
The only problem, is there any possibility to change the callers
somehow??? I even wrote the script which converts them all, but the
patch is huge.

Please see the old (2008-04-21) message I sent to lkml below, today
the diffstat is even "worse":

152 files changed, 611 insertions(+), 906 deletions(-)

and the patch size is 242k.

No? we can't?

-------------------------------------------------------------------------------
[PATCH 0.01/1] hlist_for_each_entry_xxx: kill the "pos" argument
(The actual patch is huge, 116K, I'll send it offline. This email contains
the chunk for list.h only).

COMPILE TESTED ONLY (make allyesconfig).

All hlist_for_each_entry_xxx() macros require the "pos" argument, which is not
actually needed and can be removed. See the changes in include/linux/list.h
(note that hlist_for_each_entry_safe() now does prefetch() too).

Now we should convert the callers somehow. Unfortunately, this is not always
easy. Consider this code for example:

{
struct hlist_node *tmp1, *tmp2;
hlist_for_each_entry(pos, tmp1, head,mem)
do_something(pos);

hlist_for_each_entry(pos, tmp2, head,mem)
use(tmp2);
}
The first hlist_for_each_entry is easy, but the second can't be converted
automatically because "tmp2" is used.

So, this patch

- copies these macros to "obsolete" __hlist_for_each_entry_xxx()

- changes hlist_for_each_entry_xxxx() to avoid the "struct hlist_nod*"
- converts the rest of the kernel to use either new or old macros

For example, the patch for the code above is

{
- struct hlist_node *tmp1, *tmp2;
+ struct hlist_node *tmp2;
- hlist_for_each_entry(pos, tmp1, head,mem)
+ hlist_for_each_entry(pos, head,mem)
do_something(pos);

- hlist_for_each_entry(pos, tmp2, head,mem)
+ __hlist_for_each_entry(pos, tmp2, head,mem)
use(tmp2);
}
I believe it is very easy to convert the users of the obsolete macros, but
this needs separate patches.

Except for changes in include/linux/list.h the patch was generated by this
script:

#!/usr/bin/perl -w
use strict;

my ($N_CNT, $O_CNT, @SRC, $CTXT, @CTXT);

sub say { printf STDERR "%4d: %s.\n", $., "@_" }
sub var { return $_->{$_[0]} || next for @CTXT }
sub parse_line
{
if (ord == ord '{') {
unshift @CTXT, $CTXT = {
-v_list => \@{$CTXT->{-v_list}},
-v_rexp => $CTXT->{-v_rexp},
};
}
elsif (ord == ord '}') {
say "WARN! unmatched '}'" unless $CTXT;
while (my ($v, $c) = each %$CTXT) {
my $trim = ord $v != ord '-' &&
!$c->{used} && $c->{trim} || next;
for my $tr (@$trim) {
substr($_, $tr->[1], 2, ''),
substr($_, $tr->[2], $tr->[3], '')
for $SRC[$tr->[0]];
$N_CNT++;
}
for ($SRC[$c->{decl}]) {
s/\* \s* $v \b (?: \s* , \s*)?//x || die;
s/,\s*(?=;)//; s/\bstruct\s+hlist_node\s*;//;
$_ = '' if /^\s*\\?\s*$/;
}
}
shift @CTXT; $CTXT = $CTXT[0];
}
elsif ($CTXT && /\b struct \s+ hlist_node \b ([^;]+)/x) {
my $v_list = $CTXT->{-v_list};
for (split /,/, $1) {
/^\s* \* (\w+) \s* \z/x or next;
$CTXT->{$1} = { decl => 0+@SRC };
push @$v_list, $1;
}
$CTXT->{-v_rexp} = qr/\b(@{[join '|', @$v_list]})\b/
if @$v_list;
}
elsif (/\b hlist_for_each_entry (?:_continue|_from|_safe|_rcu)? \b/xg) {
my $u = length $`;
if (/\G \s* \( .+? (, \s* (\w+) \s*)/x) {
my $tr = [0+@SRC, $u, $-[1], length $1];
if (my $v = var $2) { push @{$v->{trim}}, $tr; }
} else {
say "suspicious usage of hlist_for_each_entry_xxx()";
}
substr $_, $u, 0, '__';
$O_CNT++;
}
elsif (my $re = $CTXT && $CTXT->{-v_rexp}) {
var($1)->{used}++ while /$re/g;
}
push @SRC, $_;
}
sub diff_file
{
my $file = $_;
warn "====> $file ...\n";
($N_CNT, $O_CNT, @SRC, $CTXT, @CTXT) = 0;
open my $fd, '<', $file or die;
while (<$fd>) {
my $comm = s/(\/\*.*)//s && $1;
parse_line for split /([{}])/, $_, -1;
while ($comm) {
push @SRC, $comm;
$comm = $comm !~ /\*\// && <$fd>;
}
}
warn "WARN! unmatched '{'\n" if $CTXT;
return warn "WARN! not changed\n" unless $O_CNT;
warn "stat: $N_CNT from $O_CNT\n";
open my $diff, "|diff -up --label a/$file $file --label b/$file -";
print $diff @SRC;
}

@ARGV || die "usage: $0 path_to_kernel || list_of_files\n";
if (-d $ARGV[0]) {
chdir $ARGV[0] || die "ERR!! can't cd to $ARGV[0]\n";
warn "grep ...\n";
@ARGV = sort grep {
chomp; s/^\.\///; $_ ne 'include/linux/list.h';
} qx{grep --include='*.[ch]' -rle '\\bhlist_for_each_entry' .};
}
diff_file for @ARGV;
(it open files readonly, so can be used safely)

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

arch/arm/kernel/kprobes.c | 6 +--
arch/ia64/kernel/kprobes.c | 8 ++--
arch/powerpc/kernel/kprobes.c | 6 +--
arch/s390/kernel/kprobes.c | 6 +--
arch/sparc64/kernel/kprobes.c | 6 +--
arch/sparc64/kernel/ldc.c | 3 -
arch/x86/kernel/kprobes.c | 6 +--
arch/x86/kvm/mmu.c | 20 ++++------
block/cfq-iosched.c | 3 -
block/elevator.c | 4 +-
crypto/algapi.c | 6 +--
drivers/infiniband/core/cma.c | 3 -
drivers/infiniband/core/fmr_pool.c | 3 -
drivers/md/raid5.c | 6 +--
drivers/net/macvlan.c | 6 +--
drivers/net/pppol2tp.c | 6 +--
drivers/net/sunvnet.c | 3 -
drivers/net/wireless/zd1201.c | 7 +--
fs/dcache.c | 3 -
fs/ecryptfs/messaging.c | 5 +-
fs/fat/inode.c | 3 -
fs/gfs2/glock.c | 6 +--
fs/lockd/host.c | 17 +++------
fs/lockd/svcsubs.c | 7 +--
fs/nfsd/nfscache.c | 3 -
fs/ocfs2/dlm/dlmdebug.c | 3 -
fs/ocfs2/dlm/dlmrecovery.c | 6 +--
fs/xfs/xfs_inode.c | 3 -
include/linux/pci.h | 3 -
include/linux/pid.h | 3 -
include/net/ax25.h | 4 +-
include/net/inet_hashtables.h | 2 -
include/net/inet_timewait_sock.h | 6 +--
include/net/netrom.h | 8 ++--
include/net/sctp/sctp.h | 2 -
include/net/sock.h | 10 ++---
kernel/kprobes.c | 36 ++++++++-----------
kernel/marker.c | 15 ++------
kernel/pid.c | 3 -
kernel/sched.c | 6 +--
kernel/user.c | 3 -
net/8021q/vlan.c | 3 -
net/9p/error.c | 2 -
net/atm/lec.c | 64 +++++++++++++++--------------------
net/ax25/ax25_iface.c | 3 -
net/bridge/br_fdb.c | 17 +++------
net/can/af_can.c | 21 +++++------
net/can/proc.c | 6 +--
net/decnet/dn_table.c | 13 ++-----
net/ipv4/fib_frontend.c | 11 ++----
net/ipv4/fib_hash.c | 30 ++++++----------
net/ipv4/fib_semantics.c | 23 ++++--------
net/ipv4/fib_trie.c | 25 ++++---------
net/ipv4/inet_fragment.c | 10 ++---
net/ipv4/netfilter/nf_nat_core.c | 3 -
net/ipv6/addrlabel.c | 14 +++----
net/ipv6/ip6_fib.c | 9 +---
net/ipv6/xfrm6_tunnel.c | 12 ++----
net/netfilter/nf_conntrack_core.c | 18 +++------
net/netfilter/nf_conntrack_expect.c | 12 ++----
net/netfilter/nf_conntrack_helper.c | 14 +++----
net/netfilter/nf_conntrack_netlink.c | 12 ++----
net/netfilter/nfnetlink_log.c | 7 +--
net/netfilter/nfnetlink_queue.c | 10 ++---
net/netfilter/xt_RATEEST.c | 3 -
net/netfilter/xt_hashlimit.c | 13 ++-----
net/sched/sch_htb.c | 9 +---
net/sunrpc/auth.c | 5 +-
net/sunrpc/svcauth.c | 3 -
net/tipc/name_table.c | 8 +---
net/xfrm/xfrm_policy.c | 53 ++++++++++++----------------
net/xfrm/xfrm_state.c | 43 ++++++++---------------
72 files changed, 302 insertions(+), 439 deletions(-)
--- HL/include/linux/list.h~HLIST 2007-10-25 16:22:12.000000000 +0400
+++ HL/include/linux/list.h 2008-04-21 17:17:44.000000000 +0400
@@ -926,58 +926,54 @@ static inline void hlist_add_after_rcu(s

/**
* hlist_for_each_entry - iterate over list of given type
- * @tpos: the type * to use as a loop cursor.
- * @pos: the &struct hlist_node to use as a loop cursor.
+ * @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the hlist_node within the struct.
*/
-#define hlist_for_each_entry(tpos, pos, head, member) \
- for (pos = (head)->first; \
- pos && ({ prefetch(pos->next); 1;}) && \
- ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
- pos = pos->next)
+#define hlist_for_each_entry(pos, head, member) \
+ for (pos = (void*)(head)->first; pos && ({ \
+ prefetch(((struct hlist_node*)pos)->next); \
+ pos = hlist_entry((void*)pos, typeof(*pos), member); 1; \
+ }); pos = (void*)(pos)->member.next)

/**
* hlist_for_each_entry_continue - iterate over a hlist continuing after current point
- * @tpos: the type * to use as a loop cursor.
- * @pos: the &struct hlist_node to use as a loop cursor.
+ * @pos: the type * to use as a loop cursor.
* @member: the name of the hlist_node within the struct.
*/
-#define hlist_for_each_entry_continue(tpos, pos, member) \
- for (pos = (pos)->next; \
- pos && ({ prefetch(pos->next); 1;}) && \
- ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
- pos = pos->next)
+#define hlist_for_each_entry_continue(pos, member) \
+ for (; (pos = (void*)(pos)->member.next) && ({ \
+ prefetch(((struct hlist_node*)pos)->next); \
+ pos = hlist_entry((void*)pos, typeof(*pos), member); 1; \
+ }); )

/**
* hlist_for_each_entry_from - iterate over a hlist continuing from current point
- * @tpos: the type * to use as a loop cursor.
- * @pos: the &struct hlist_node to use as a loop cursor.
+ * @pos: the type * to use as a loop cursor.
* @member: the name of the hlist_node within the struct.
*/
-#define hlist_for_each_entry_from(tpos, pos, member) \
- for (; pos && ({ prefetch(pos->next); 1;}) && \
- ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
- pos = pos->next)
+#define hlist_for_each_entry_from(pos, member) \
+ for (pos = pos ? (void*)&(pos)->member.next : pos; pos && ({ \
+ prefetch(((struct hlist_node*)pos)->next); \
+ pos = hlist_entry((void*)pos, typeof(*pos), member); 1; \
+ }); pos = (void*)(pos)->member.next)

/**
* hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
- * @tpos: the type * to use as a loop cursor.
- * @pos: the &struct hlist_node to use as a loop cursor.
+ * @pos: the type * to use as a loop cursor.
* @n: another &struct hlist_node to use as temporary storage
* @head: the head for your list.
* @member: the name of the hlist_node within the struct.
*/
-#define hlist_for_each_entry_safe(tpos, pos, n, head, member) \
- for (pos = (head)->first; \
- pos && ({ n = pos->next; 1; }) && \
- ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
- pos = n)
+#define hlist_for_each_entry_safe(pos, n, head, member) \
+ for (pos = (void*)(head)->first; pos && ({ \
+ n = ((struct hlist_node*)pos)->next; prefetch(n); \
+ pos = hlist_entry((void*)pos, typeof(*pos), member); 1; \
+ }); pos = (void*)n)

/**
* hlist_for_each_entry_rcu - iterate over rcu list of given type
- * @tpos: the type * to use as a loop cursor.
- * @pos: the &struct hlist_node to use as a loop cursor.
+ * @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the hlist_node within the struct.
*
@@ -985,7 +981,38 @@ static inline void hlist_add_after_rcu(s
* the _rcu list-mutation primitives such as hlist_add_head_rcu()
* as long as the traversal is guarded by rcu_read_lock().
*/
-#define hlist_for_each_entry_rcu(tpos, pos, head, member) \
+#define hlist_for_each_entry_rcu(pos, head, member) \
+ for (pos = (void*)(head)->first; rcu_dereference(pos) && ({ \
+ prefetch(((struct hlist_node*)pos)->next); \
+ pos = hlist_entry((void*)pos, typeof(*pos), member); 1; \
+ }); pos = (void*)(pos)->member.next)
+
+/* -------- Obsolete, to be removed soon, do not use -------- */
+
+#define __hlist_for_each_entry(tpos, pos, head, member) \
+ for (pos = (head)->first; \
+ pos && ({ prefetch(pos->next); 1;}) && \
+ ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+ pos = pos->next)
+
+#define __hlist_for_each_entry_continue(tpos, pos, member) \
+ for (pos = (pos)->next; \
+ pos && ({ prefetch(pos->next); 1;}) && \
+ ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+ pos = pos->next)
+
+#define __hlist_for_each_entry_from(tpos, pos, member) \
+ for (; pos && ({ prefetch(pos->next); 1;}) && \
+ ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+ pos = pos->next)
+
+#define __hlist_for_each_entry_safe(tpos, pos, n, head, member) \
+ for (pos = (head)->first; \
+ pos && ({ n = pos->next; 1; }) && \
+ ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
+ pos = n)
+
+#define __hlist_for_each_entry_rcu(tpos, pos, head, member) \
for (pos = (head)->first; \
rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \


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