From: Jakub Kicinski <kuba@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-wireless <linux-wireless@vger.kernel.org>,
alsa-devel@alsa-project.org, "KVM list" <kvm@vger.kernel.org>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
linux-iio@vger.kernel.org, nouveau@lists.freedesktop.org,
"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
dri-devel <dri-devel@lists.freedesktop.org>,
"Cristiano Giuffrida" <c.giuffrida@vu.nl>,
"Bos, H.J." <h.j.bos@vu.nl>,
linux1394-devel@lists.sourceforge.net, drbd-dev@lists.linbit.com,
linux-arch <linux-arch@vger.kernel.org>,
CIFS <linux-cifs@vger.kernel.org>,
linux-aspeed@lists.ozlabs.org,
linux-scsi <linux-scsi@vger.kernel.org>,
linux-rdma <linux-rdma@vger.kernel.org>,
linux-staging@lists.linux.dev,
"amd-gfx list" <amd-gfx@lists.freedesktop.org>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
intel-wired-lan@lists.osuosl.org,
kgdb-bugreport@lists.sourceforge.net,
bcm-kernel-feedback-list@broadcom.com,
"Dan Carpenter" <dan.carpenter@oracle.com>,
"Linux Media Mailing List" <linux-media@vger.kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Arnd Bergman" <arnd@arndb.de>,
"Linux PM" <linux-pm@vger.kernel.org>,
intel-gfx <intel-gfx@lists.freedesktop.org>,
"Brian Johannesmeyer" <bjohannesmeyer@gmail.com>,
"Nathan Chancellor" <nathan@kernel.org>,
dma <dmaengine@vger.kernel.org>,
"Christophe JAILLET" <christophe.jaillet@wanadoo.fr>,
"Jakob Koschel" <jakobkoschel@gmail.com>,
v9fs-developer@lists.sourceforge.net,
linux-tegra <linux-tegra@vger.kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
linux-sgx@vger.kernel.org,
linux-block <linux-block@vger.kernel.org>,
Netdev <netdev@vger.kernel.org>,
linux-usb@vger.kernel.org, samba-technical@lists.samba.org,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Linux F2FS Dev Mailing List"
<linux-f2fs-devel@lists.sourceforge.net>,
tipc-discussion@lists.sourceforge.net,
"Linux Crypto Mailing List" <linux-crypto@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-mediatek@lists.infradead.org,
"Andrew Morton" <akpm@linux-foundation.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"Christian König" <christian.koenig@amd.com>,
"Mike Rapoport" <rppt@kernel.org>
Subject: Re: [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr
Date: Mon, 28 Feb 2022 22:32:28 -0800 [thread overview]
Message-ID: <20220228223228.24cf3fd4@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net> (raw)
In-Reply-To: <CAHk-=whLK11HyvpUtEftOjc3Gup2V77KpAQ2fycj3uai=qceHw@mail.gmail.com>
On Mon, 28 Feb 2022 16:41:04 -0800 Linus Torvalds wrote:
> So yes, initially my idea had been to just move the iterator entirely
> inside the macro. But specifying the type got so ugly that I think
> that
>
> typeof (pos) pos
>
> trick inside the macro really ends up giving us the best of all worlds:
>
> (a) let's us keep the existing syntax and code for all the nice cases
> that did everything inside the loop anyway
>
> (b) gives us a nice warning for any normal use-after-loop case
> (unless you explicitly initialized it like that
> sgx_mmu_notifier_release() function did for no good reason
>
> (c) also guarantees that even if you don't get a warning,
> non-converted (or newly written) bad code won't actually _work_
>
> so you end up getting the new rules without any ambiguity or mistaken
I presume the goal is that we can do this without changing existing
code? Otherwise actually moving the iterator into the loop body would
be an option, by creating a different hidden variable:
#define list_iter(head) \
for (struct list head *_l = (head)->next; _l != (head); _l = _l->next)
#define list_iter_entry(var, member) \
list_entry(_l, typeof(*var), member)
list_iter(&p->a_head) {
struct entry *e = list_iter_entry(e, a_member);
/* use e->... */
}
Or we can slide into soft insanity and exploit one of Kees'es tricks
to encode the type of the entries "next to" the head:
#define LIST_HEAD_MEM(name, type) \
union { \
struct list_head name; \
type *name ## _entry; \
}
struct entry {
struct list_head a_member;
};
struct parent {
LIST_HEAD_MEM(a_head, struct entry);
};
#define list_for_each_magic(pos, head, member) \
for (typeof(**(head ## _entry)) *pos = list_first_entry(head, typeof(**(head ## _entry)), member); \
&pos->member != (head); \
pos = list_next_entry(pos, member))
list_for_each_magic(e, &p->a_head, a_member) {
/* use e->... */
}
I'll show myself out...
next prev parent reply other threads:[~2022-03-01 6:33 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-28 11:08 [PATCH 0/6] Remove usage of list iterator past the loop body Jakob Koschel
2022-02-28 11:08 ` [PATCH 1/6] drivers: usb: remove " Jakob Koschel
2022-02-28 11:24 ` Dan Carpenter
2022-02-28 12:03 ` Jakob Koschel
2022-02-28 13:18 ` Dan Carpenter
2022-02-28 18:20 ` Joe Perches
2022-03-01 5:52 ` Dan Carpenter
2022-02-28 11:08 ` [PATCH 2/6] treewide: remove using list iterator after loop body as a ptr Jakob Koschel
2022-02-28 11:20 ` Greg KH
2022-02-28 12:06 ` Jakob Koschel
2022-03-01 17:37 ` Greg KH
2022-02-28 12:19 ` Christian König
2022-02-28 19:56 ` Linus Torvalds
2022-02-28 20:03 ` Linus Torvalds
2022-02-28 20:10 ` Linus Torvalds
2022-02-28 20:14 ` Linus Torvalds
2022-02-28 20:53 ` Segher Boessenkool
2022-02-28 20:16 ` Matthew Wilcox
2022-02-28 20:27 ` Johannes Berg
2022-02-28 20:41 ` Linus Torvalds
2022-02-28 20:37 ` Linus Torvalds
2022-02-28 23:26 ` Matthew Wilcox
2022-03-01 0:45 ` Linus Torvalds
2022-03-01 0:57 ` Linus Torvalds
2022-03-01 18:14 ` Kees Cook
2022-03-01 18:47 ` Linus Torvalds
2022-03-01 19:01 ` Matthew Wilcox
2022-03-01 3:03 ` David Laight
2022-02-28 21:47 ` Jakob Koschel
2022-03-01 0:41 ` Linus Torvalds
2022-03-01 6:32 ` Jakub Kicinski [this message]
2022-03-01 11:28 ` Jakob Koschel
2022-03-01 17:36 ` Greg KH
2022-03-01 17:40 ` Jakob Koschel
2022-03-01 17:58 ` Greg KH
2022-03-01 18:21 ` Kees Cook
2022-03-02 9:31 ` Xiaomeng Tong
2022-03-02 14:04 ` David Laight
2022-03-03 2:27 ` Xiaomeng Tong
2022-03-03 4:58 ` David Laight
2022-03-03 7:26 ` Xiaomeng Tong
2022-03-03 9:30 ` David Laight
2022-03-03 12:37 ` Xiaomeng Tong
2022-03-03 12:18 ` [Kgdb-bugreport] " Daniel Thompson
2022-03-04 6:59 ` Xiaomeng Tong
2022-03-03 7:32 ` Jakob Koschel
2022-03-03 8:30 ` Xiaomeng Tong
2022-03-03 8:38 ` Xiaomeng Tong
2022-02-28 20:07 ` Christian König
2022-02-28 20:42 ` James Bottomley
2022-02-28 20:56 ` Christian König
2022-02-28 21:13 ` James Bottomley
2022-03-01 7:03 ` Christian König
2022-02-28 22:05 ` Jakob Koschel
2022-02-28 21:18 ` Jeffrey Walton
2022-02-28 21:59 ` Mike Rapoport
2022-02-28 22:28 ` James Bottomley
2022-02-28 22:50 ` Barnabás Pőcze
2022-03-01 0:30 ` Segher Boessenkool
2022-03-01 0:54 ` Linus Torvalds
2022-03-01 19:06 ` Linus Torvalds
2022-03-01 19:42 ` Linus Torvalds
2022-03-01 22:58 ` David Laight
2022-03-01 23:03 ` Linus Torvalds
2022-03-01 23:19 ` David Laight
2022-03-01 23:55 ` Linus Torvalds
2022-03-02 9:29 ` Rasmus Villemoes
2022-03-02 20:07 ` Kees Cook
2022-03-02 20:18 ` Linus Torvalds
2022-03-02 20:59 ` Kees Cook
2022-03-03 8:37 ` Dan Carpenter
2022-03-03 10:56 ` Dan Carpenter
2022-03-01 2:15 ` David Laight
2022-02-28 13:13 ` Dan Carpenter
2022-02-28 11:08 ` [PATCH 3/6] treewide: fix incorrect use to determine if list is empty Jakob Koschel
2022-02-28 11:38 ` Dan Carpenter
2022-02-28 11:08 ` [PATCH 4/6] drivers: remove unnecessary use of list iterator variable Jakob Koschel
2022-02-28 11:08 ` [PATCH 5/6] treewide: remove dereference of list iterator after loop body Jakob Koschel
2022-02-28 11:08 ` [PATCH 6/6] treewide: remove check of list iterator against head past the " Jakob Koschel
2022-02-28 11:22 ` Dominique Martinet
2022-02-28 13:12 ` Dan Carpenter
2022-03-01 20:36 ` Linus Torvalds
2022-03-02 17:14 ` [Intel-gfx] " Tvrtko Ursulin
2022-03-07 15:00 ` [PATCH 0/6] Remove usage of list iterator " Dan Carpenter
2022-03-07 15:26 ` David Laight
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220228223228.24cf3fd4@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net \
--to=kuba@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=alsa-devel@alsa-project.org \
--cc=amd-gfx@lists.freedesktop.org \
--cc=andriy.shevchenko@linux.intel.com \
--cc=arnd@arndb.de \
--cc=bcm-kernel-feedback-list@broadcom.com \
--cc=bjohannesmeyer@gmail.com \
--cc=c.giuffrida@vu.nl \
--cc=christian.koenig@amd.com \
--cc=christophe.jaillet@wanadoo.fr \
--cc=dan.carpenter@oracle.com \
--cc=dmaengine@vger.kernel.org \
--cc=drbd-dev@lists.linbit.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=gustavo@embeddedor.com \
--cc=h.j.bos@vu.nl \
--cc=intel-gfx@lists.freedesktop.org \
--cc=intel-wired-lan@lists.osuosl.org \
--cc=jakobkoschel@gmail.com \
--cc=jgg@ziepe.ca \
--cc=keescook@chromium.org \
--cc=kgdb-bugreport@lists.sourceforge.net \
--cc=kvm@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-aspeed@lists.ozlabs.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-cifs@vger.kernel.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-f2fs-devel@lists.sourceforge.net \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=linux-pm@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=linux-sgx@vger.kernel.org \
--cc=linux-staging@lists.linux.dev \
--cc=linux-tegra@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=linux-wireless@vger.kernel.org \
--cc=linux1394-devel@lists.sourceforge.net \
--cc=linux@rasmusvillemoes.dk \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=nathan@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=nouveau@lists.freedesktop.org \
--cc=rppt@kernel.org \
--cc=samba-technical@lists.samba.org \
--cc=tglx@linutronix.de \
--cc=tipc-discussion@lists.sourceforge.net \
--cc=torvalds@linux-foundation.org \
--cc=v9fs-developer@lists.sourceforge.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).