Date: Fri, 17 May 2024 12:32:51 -0700 From: John Baldwin <jhb@FreeBSD.org> To: Emmanuel Vadot <manu@bidouilliste.com> Cc: Emmanuel Vadot <manu@FreeBSD.org>, src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: cff79fd02636 - main - linuxkpi: Fix spin_lock_init Message-ID: <0f2c4189-e259-4bd8-ad31-212a8df0e1b5@FreeBSD.org> In-Reply-To: <20240517183350.e45f54df07f670980d5a51c3@bidouilliste.com> References: <202405170559.44H5xD7d019861@gitrepo.freebsd.org> <2cd3e698-1b42-4e7f-93a0-aacccb55c8d6@FreeBSD.org> <20240517183350.e45f54df07f670980d5a51c3@bidouilliste.com>
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On 5/17/24 9:33 AM, Emmanuel Vadot wrote: > On Fri, 17 May 2024 09:07:53 -0700 > John Baldwin <jhb@FreeBSD.org> wrote: > >> On 5/16/24 10:59 PM, Emmanuel Vadot wrote: >>> The branch main has been updated by manu: >>> >>> URL: https://cgit.FreeBSD.org/src/commit/?id=cff79fd02636f34010d8b835cc9e55401fa76e74 >>> >>> commit cff79fd02636f34010d8b835cc9e55401fa76e74 >>> Author: Emmanuel Vadot <manu@FreeBSD.org> >>> AuthorDate: 2024-05-17 04:52:53 +0000 >>> Commit: Emmanuel Vadot <manu@FreeBSD.org> >>> CommitDate: 2024-05-17 05:58:59 +0000 >>> >>> linuxkpi: Fix spin_lock_init >>> >>> Some linux code re-init some spinlock so add MTX_NEW to mtx_init. >>> >>> Reported by: David Wolfskill <david@catwhisker.org> >>> Fixes: ae38a1a1bfdf ("linuxkpi: spinlock: Simplify code") >>> --- >>> sys/compat/linuxkpi/common/include/linux/spinlock.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/sys/compat/linuxkpi/common/include/linux/spinlock.h b/sys/compat/linuxkpi/common/include/linux/spinlock.h >>> index 3f6eb4bb70f6..2992e41c9c02 100644 >>> --- a/sys/compat/linuxkpi/common/include/linux/spinlock.h >>> +++ b/sys/compat/linuxkpi/common/include/linux/spinlock.h >>> @@ -140,7 +140,7 @@ typedef struct mtx spinlock_t; >>> #define spin_lock_name(name) _spin_lock_name(name, __FILE__, __LINE__) >>> >>> #define spin_lock_init(lock) mtx_init(lock, spin_lock_name("lnxspin"), \ >>> - NULL, MTX_DEF | MTX_NOWITNESS) >>> + NULL, MTX_DEF | MTX_NOWITNESS | MTX_NEW) >>> >>> #define spin_lock_destroy(_l) mtx_destroy(_l) >> >> This is only ok because of MTX_NOWITNESS. Reiniting locks without destroying >> them corrupts the internal linked lists in WITNESS for locks using witness. >> That may warrant a comment here explaining why we disable witness. > > I'll try to look at what linux expect for spinlocks, it could also be > that we need to do this because some drivers via linuxkpi does weird > things ... > >> It might be nice to add an extension to the various lock inits for code that >> wants to opt-int to using WITNESS where a name can be passed. Using those would >> be relatively small diffs in the client code and let select locks opt into >> using WITNESS. You could make it work by adding an optional second argument >> to spin_lock_init, etc. that takes the name. > > We can't change spin_lock_init, we need to follow linux api here. You can use macro magic to add support for an optional second argument. #define _spin_lock_init2(lock, name) mtx_init(lock, name, NULL, MTX_DEF) #define _spin_lock_init1(lock) mtx_init(lock, spin_lock_name("lnxspin"), ...) #define _spin_lock_init_macro(lock, name, NAME, ...) NAME #define spin_lock_init(...) \ _spin_lock_init_macro(__VA_ARGS__, _spin_lock_init2, _spin_lock_init1)(__VA_ARGS__) Then you can choose to specifically annotate certain locks with a name instead in which case they will use WITNESS. -- John Baldwin
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