Re: git: b75062f23431 - main - riscv: Fix thread0.td_kstack_pages init
Date: Thu, 19 Jan 2023 00:57:28 UTC
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: > > > > > > > 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=b75062f23431fbabef1e7d665cae270b144f71b1 > > > > > > 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 from > > > 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. > > > > 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> > > I do agree, however, that the current interface is less than ideal... > > > > 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 stands. > > > > I think it's a good point, but the current way is likely the least-bad way > to accomplish things. > > 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 otherwise > 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