Date: Sun, 21 May 2023 10:14:26 -0700 From: Mark Millard <marklmi@yahoo.com> To: hselasky@freebsd.org, dev-commits-src-main@freebsd.org Subject: RE: git: 805d759338a2 - main - mlx4: Move DEFINE_MUTEX() outside function body. Message-ID: <C375C14D-C185-415A-A2B4-82123F1EA5FF@yahoo.com> References: <C375C14D-C185-415A-A2B4-82123F1EA5FF.ref@yahoo.com>
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Hans Petter Selasky <hselasky_at_freebsd.org> wrote on Date: Sun, 21 May 2023 16:57:47 UTC : > On 5/21/23 18:33, Jessica Clarke wrote: > > On 21 May 2023, at 17:21, Hans Petter Selasky <hselasky@FreeBSD.org> = wrote: > >> > >> The branch main has been updated by hselasky: > >> > >> URL: = https://cgit.FreeBSD.org/src/commit/?id=3D805d759338a2be939fffc8bf3f25cfaa= b981a9be > >> > >> commit 805d759338a2be939fffc8bf3f25cfaab981a9be > >> Author: Hans Petter Selasky <hselasky@FreeBSD.org> > >> AuthorDate: 2023-05-21 11:25:28 +0000 > >> Commit: Hans Petter Selasky <hselasky@FreeBSD.org> > >> CommitDate: 2023-05-21 16:20:16 +0000 > >> > >> mlx4: Move DEFINE_MUTEX() outside function body. > >> > >> Move static mutex declaration outside function body, to avoid = global > >> variables being declared on the stack, when using SYSINITs. > >=20 > > What? This is nonsense. It=E2=80=99s not on the stack either way = round. > >=20 > > Please revert this. > >=20 > > Jess >=20 > Hi Jess, >=20 > I think this is a false positive of yours. You need to look through = all=20 > the macros used there. >=20 > Basically DEFINE_MUTEX() expands to a bunch of structures, which are = not=20 > in any block. DEFINE_MUTEX is from/for linux related code: # grep -r "define.*DEFINE_MUTEX" /usr/main-src/sys/ | more /usr/main-src/sys/compat/linuxkpi/common/include/linux/mutex.h:#define = DEFINE_MUTEX(lock) \ and looks like: #define DEFINE_MUTEX(lock) = \ mutex_t lock; = \ SX_SYSINIT_FLAGS(lock, &(lock).sx, mutex_name(#lock), SX_DUPOK) > The "static" you see in patch just covers the first mutex structure. >=20 > SYSINITs use "static" in front of all structure definitions. > If you want to change from static structures to global symbols, then = my=20 > change is correct. >=20 > Before: >=20 > static DEFINE_MUTEX(xxx); >=20 > Expands to something like: >=20 > static struct yyy xxx; static struct sysinit zzz; .... Not true. > If you want to change from "static struct sysinit zzz;" to "extern=20 > struct sysinit zzz" and also initialize the structure there, then that=20= > won't work, based on what I currently know about C-programming. I = tried,=20 > but clang gave me a warning about it. >=20 >=20 >=20 > You can't declare global variables inside a function or it is not good=20= > style. >=20 >=20 >=20 > =46rom what I can see, this location is the only place I've come = accross=20 > in the FreeBSD kernel, where a SYSINIT() is used inside a function, = and=20 > I thought I would just move that outside the function instead. >=20 > This change also allows for: >=20 > https://reviews.freebsd.org/D40193 >=20 =3D=3D=3D Mark Millard marklmi at yahoo.com
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