Re: [committed] hppa: Drop 16-byte pthread lock alignment

[John David Anglin <dave.anglin@bell.net>]

After some discussion, I decided it would be best to revert this change for now.

Commit 500054974667be3153ed760152ea0153df33c3d0 reverts " hppa: Drop 16-byte pthread lock alignment"
(commits c4468cd3995b4236ea886901109b194641132b08 and ab991a3d1b401ded6bd4f027352da8262b021a11).

Dave

On 2023-03-26 5:22 p.m., John David Anglin wrote:
> hppa: Drop 16-byte pthread lock alignment
>
> Linux threads were removed about 12 years ago and the current
> nptl implementation only requires 4-byte alignment for pthread
> locks.
>
> The 16-byte alignment causes various issues. For example in
> building ignition-msgs, we have:
>
> /usr/include/google/protobuf/map.h:124:37: error: static assertion failed
>    124 |   static_assert(alignof(value_type) <= 8, "");
>        |                 ~~~~~~~~~~~~~~~~~~~~^~~~
>
> This is caused by the 16-byte pthread lock alignment.
>
> Signed-off-by: John David Anglin <dave.anglin@bell.net>
> ---
>
> diff --git a/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h b/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
> index 999195c5b0..c1a46d66d0 100644
> --- a/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
> +++ b/sysdeps/hppa/nptl/bits/pthreadtypes-arch.h
> @@ -40,7 +40,7 @@
>   #define __SIZEOF_PTHREAD_RWLOCK_T 64
>   #define __SIZEOF_PTHREAD_RWLOCKATTR_T 8
>   
> -#define __LOCK_ALIGNMENT __attribute__ ((__aligned__(16)))
> +#define __LOCK_ALIGNMENT
>   #define __ONCE_ALIGNMENT
>   
>   #endif	/* bits/pthreadtypes.h */
> diff --git a/sysdeps/hppa/nptl/bits/struct_rwlock.h b/sysdeps/hppa/nptl/bits/struct_rwlock.h
> index e83b4aab52..59bc9fe76f 100644
> --- a/sysdeps/hppa/nptl/bits/struct_rwlock.h
> +++ b/sysdeps/hppa/nptl/bits/struct_rwlock.h
> @@ -25,8 +25,14 @@ struct __pthread_rwlock_arch_t
>     /* In the old Linuxthreads pthread_rwlock_t, this is the
>        start of the 4-word 16-byte aligned lock structure. The
>        next four words are all set to 1 by the Linuxthreads
> -     PTHREAD_RWLOCK_INITIALIZER. We ignore them in NPTL.  */
> -  int __compat_padding[4] __attribute__ ((__aligned__(16)));
> +     PTHREAD_RWLOCK_INITIALIZER. We ignore them in NPTL.
> +
> +     The 16-byte aligned lock stucture causes various pthread
> +     structures to be over aligned. This causes some builds
> +     to fail which assume a maximum alignment of 8 bytes.
> +     Linuxthreads has been removed for 12 years, so drop
> +     alignment of lock structure.  */
> +  int __compat_padding[4];
>     unsigned int __readers;
>     unsigned int __writers;
>     unsigned int __wrphase_futex;


-- 
John David Anglin  dave.anglin@bell.net