Date: Thu, 19 Jan 2023 00:57:28 +0000 From: Brooks Davis <brooks@freebsd.org> To: Warner Losh <imp@bsdimp.com> Cc: Mitchell Horne <mhorne@freebsd.org>, Brooks Davis <brooks@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: b75062f23431 - main - riscv: Fix thread0.td_kstack_pages init Message-ID: <Y8iVeJsN1b8RnhId@spindle.one-eyed-alien.net> In-Reply-To: <CANCZdfrMm0Kd46pfOYUaiAU%2BsMvYecU0whDH2jH0ck3C-Jjy0w@mail.gmail.com> References: <202301171638.30HGcP3C091184@gitrepo.freebsd.org> <b2a60e9a-c918-5a88-5eb9-5d8322ca2326@freebsd.org> <CANCZdfrMm0Kd46pfOYUaiAU%2BsMvYecU0whDH2jH0ck3C-Jjy0w@mail.gmail.com>
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On Wed, Jan 18, 2023 at 04:53:51PM -0700, Warner Losh wrote: > On Wed, Jan 18, 2023 at 3:07 PM Mitchell Horne <mhorne@freebsd.org> wrote: >=20 > > > > > > On 1/17/23 12:38, Brooks Davis wrote: > > > The branch main has been updated by brooks: > > > > > > URL: > > https://cgit.FreeBSD.org/src/commit/?id=3Db75062f23431fbabef1e7d665cae2= 70b144f71b1 > > > > > > commit b75062f23431fbabef1e7d665cae270b144f71b1 > > > Author: Brooks Davis <brooks@FreeBSD.org> > > > AuthorDate: 2023-01-17 16:36:15 +0000 > > > Commit: Brooks Davis <brooks@FreeBSD.org> > > > CommitDate: 2023-01-17 16:37:42 +0000 > > > > > > riscv: Fix thread0.td_kstack_pages init > > > > > > Commit 0ef3ca7ae37c70e9dc83475dc2e68e98e1c2a418 initialized > > > thread0.td_kstack_pages to KSTACK_PAGES. Due to the lack of an > > > include of opt_kstack_pages.h it used the fallback value of 4 fr= om > > > machine/param.h. > > > > Does this mean that we could/should include opt_kstack_pages.h within > > machine/param.h (under #ifdef _KERNEL)? This header is both a consumer > > and provider of the KSTACK_PAGES definition, by virtue of the #ifndef. I > > think the hidden dependency should be avoided, if possible. > > >=20 > No. Including opt_XXXX.h is never OK in our .h files. They are used in too > many places, some of which "cheat" and define _KERNEL becuse, well, they > need to get to the kernel bits.... That will break... We could potentially use the __has_include extension. I don't think we care about building the kernel with a compiler that isn't clang or gcc and the usage pattern defined by gcc is safe for compilers that don't define it. We could do something like: #ifdef _KERNEL #ifndef KSTACK_PAGES #ifdef __has_include #if __has_include("opt_kstack_pages.h") #include "opt_kstack_pages.h" #endif #endif #endif #endif <old #ifndef KSTACK_PAGES code> >=20 > I do agree, however, that the current interface is less than ideal... >=20 >=20 > > Of course, the problem at hand has been fixed and we want to keep direct > > consumers of KSTACK_PAGES to a minimum, but I think the point still sta= nds. > > >=20 > I think it's a good point, but the current way is likely the least-bad way > to accomplish things. >=20 > It would be much better if we could remove it from machine/param.h and > opt_XXX.h always defines it, even the default value when it's not otherwi= se > specified. However, we don't (currently) have a way to set default values > in config(8). We could add it, since the efforts at config++ have thus far > fallen flat.... I think this is probably the better direction to move. There aren't any in-tree uses of KSTACK_PAGES so removing the definition should be fine. -- Brooks
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