The printk header file includes ratelimit_types.h for its __ratelimit()
based usage. It is required for the static initializer used in
printk_ratelimited(). It uses a raw_spinlock_t and includes the
spinlock_types.h.

PREEMPT_RT substitutes spinlock_t with a rtmutex based implementation and so
its spinlock_t implmentation (provided by spinlock_rt.h) includes rtmutex.h and
atomic.h which leads to recursive includes where defines are missing.

By including only the raw_spinlock_t defines it avoids the atomic.h
related includes at this stage.

An example on powerpc:

|  CALL    scripts/atomic/check-atomics.sh
|In file included from include/linux/bug.h:5,
|                 from include/linux/page-flags.h:10,
|                 from kernel/bounds.c:10:
|arch/powerpc/include/asm/page_32.h: In function ‘clear_page’:
|arch/powerpc/include/asm/bug.h:87:4: error: implicit declaration of function â=80=98__WARNâ=80=99 [-Werror=3Dimplicit-function-declaration]
|   87 |    __WARN();    \
|      |    ^~~~~~
|arch/powerpc/include/asm/page_32.h:48:2: note: in expansion of macro ‘WARN_ONâ€=99
|   48 |  WARN_ON((unsigned long)addr & (L1_CACHE_BYTES - 1));
|      |  ^~~~~~~
|arch/powerpc/include/asm/bug.h:58:17: error: invalid application of ‘sizeofâ€=99 to incomplete type ‘struct bug_entryâ€=99
|   58 |     "i" (sizeof(struct bug_entry)), \
|      |                 ^~~~~~
|arch/powerpc/include/asm/bug.h:89:3: note: in expansion of macro ‘BUG_ENTRYâ€=99
|   89 |   BUG_ENTRY(PPC_TLNEI " %4, 0",   \
|      |   ^~~~~~~~~
|arch/powerpc/include/asm/page_32.h:48:2: note: in expansion of macro ‘WARN_ONâ€=99
|   48 |  WARN_ON((unsigned long)addr & (L1_CACHE_BYTES - 1));
|      |  ^~~~~~~
|In file included from arch/powerpc/include/asm/ptrace.h:298,
|                 from arch/powerpc/include/asm/hw_irq.h:12,
|                 from arch/powerpc/include/asm/irqflags.h:12,
|                 from include/linux/irqflags.h:16,
|                 from include/asm-generic/cmpxchg-local.h:6,
|                 from arch/powerpc/include/asm/cmpxchg.h:526,
|                 from arch/powerpc/include/asm/atomic.h:11,
|                 from include/linux/atomic.h:7,
|                 from include/linux/rwbase_rt.h:6,
|                 from include/linux/rwlock_types.h:55,
|                 from include/linux/spinlock_types.h:74,
|                 from include/linux/ratelimit_types.h:7,
|                 from include/linux/printk.h:10,
|                 from include/asm-generic/bug.h:22,
|                 from arch/powerpc/include/asm/bug.h:109,
|                 from include/linux/bug.h:5,
|                 from include/linux/page-flags.h:10,
|                 from kernel/bounds.c:10:
|include/linux/thread_info.h: In function â=80=98copy_overflowâ=80=99:
|include/linux/thread_info.h:210:2: error: implicit declaration of function â=80=98WARNâ=80=99 [-Werror=3Dimplicit-function-declaration]
|  210 |  WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
|      |  ^~~~

The WARN / BUG include pulls in printk.h and then ptrace.h expects WARN
(from bug.h) which is not yet complete. Even hw_irq.h has WARN_ON()
statements.

On POWERPC64 there are missing atomic64 defines while building 32bit
VDSO:
|  VDSO32C arch/powerpc/kernel/vdso32/vgettimeofday.o
|In file included from include/linux/atomic.h:80,
|                 from include/linux/rwbase_rt.h:6,
|                 from include/linux/rwlock_types.h:55,
|                 from include/linux/spinlock_types.h:74,
|                 from include/linux/ratelimit_types.h:7,
|                 from include/linux/printk.h:10,
|                 from include/linux/kernel.h:19,
|                 from arch/powerpc/include/asm/page.h:11,
|                 from arch/powerpc/include/asm/vdso/gettimeofday.h:5,
|                 from include/vdso/datapage.h:137,
|                 from lib/vdso/gettimeofday.c:5,
|                 from <command-line>:
|include/linux/atomic-arch-fallback.h: In function ‘arch_atomic64_incâ€=99:
|include/linux/atomic-arch-fallback.h:1447:2: error: implicit declaration of function ‘arch_atomic64_add’; did you mean ‘arch_atomic_add’? [-Werror=3Dimpl
|icit-function-declaration]
| 1447 |  arch_atomic64_add(1, v);
|      |  ^~~~~~~~~~~~~~~~~
|      |  arch_atomic_add

The generic fallback is not included, atomics itself are not used. If
kernel.h does not include printk.h then it comes later from the bug.h
include.

Allow asm/spinlock_types.h to be included from
linux/spinlock_types_raw.h.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211129174654.668506-12-bigeasy@linutronix.de