[03/13] nptl: Export __libc_multiple_threads from libc as an internal symbol

  This allows the elimination of the __libc_multiple_threads_ptr
variable in libpthread and its initialization procedure.
---
 nptl/Versions                           |  1 +
 nptl/allocatestack.c                    |  4 ++--
 nptl/libc_multiple_threads.c            |  3 ++-
 nptl/libc_pthread_init.c                | 11 -----------
 nptl/nptl-init.c                        | 10 +---------
 nptl/pthreadP.h                         |  6 +-----
 nptl/pthread_cancel.c                   |  2 +-
 sysdeps/unix/sysv/linux/single-thread.h |  6 +++++-
 8 files changed, 13 insertions(+), 30 deletions(-)
  

On 5/6/21 2:10 PM, Florian Weimer via Libc-alpha wrote:
> This allows the elimination of the __libc_multiple_threads_ptr
> variable in libpthread and its initialization procedure.

LGTM.

Tested on x86_64 and i686 without regression.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  nptl/Versions                           |  1 +
>  nptl/allocatestack.c                    |  4 ++--
>  nptl/libc_multiple_threads.c            |  3 ++-
>  nptl/libc_pthread_init.c                | 11 -----------
>  nptl/nptl-init.c                        | 10 +---------
>  nptl/pthreadP.h                         |  6 +-----
>  nptl/pthread_cancel.c                   |  2 +-
>  sysdeps/unix/sysv/linux/single-thread.h |  6 +++++-
>  8 files changed, 13 insertions(+), 30 deletions(-)
> 
> diff --git a/nptl/Versions b/nptl/Versions
> index f950b77969..fb15a7e8eb 100644
> --- a/nptl/Versions
> +++ b/nptl/Versions
> @@ -305,6 +305,7 @@ libc {
>      __libc_cleanup_pop_restore;
>      __libc_cleanup_push_defer;
>      __libc_dl_error_tsd;
> +    __libc_multiple_threads;
>      __libc_pthread_init;
>      __lll_clocklock_elision;
>      __lll_lock_elision;
> diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
> index 8aaba088b1..059786192e 100644
> --- a/nptl/allocatestack.c
> +++ b/nptl/allocatestack.c
> @@ -477,7 +477,7 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
>        /* This is at least the second thread.  */
>        pd->header.multiple_threads = 1;
>  #ifndef TLS_MULTIPLE_THREADS_IN_TCB
> -      __pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
> +      __pthread_multiple_threads = __libc_multiple_threads = 1;
>  #endif
>  
>  #ifdef NEED_DL_SYSINFO
> @@ -598,7 +598,7 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
>  	  /* This is at least the second thread.  */
>  	  pd->header.multiple_threads = 1;
>  #ifndef TLS_MULTIPLE_THREADS_IN_TCB
> -	  __pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
> +	  __pthread_multiple_threads = __libc_multiple_threads = 1;
>  #endif
>  
>  #ifdef NEED_DL_SYSINFO
> diff --git a/nptl/libc_multiple_threads.c b/nptl/libc_multiple_threads.c
> index 60328023cd..a0e7932c26 100644
> --- a/nptl/libc_multiple_threads.c
> +++ b/nptl/libc_multiple_threads.c
> @@ -23,6 +23,7 @@
>  /* Variable set to a nonzero value either if more than one thread runs or ran,
>     or if a single-threaded process is trying to cancel itself.  See
>     nptl/descr.h for more context on the single-threaded process case.  */
> -int __libc_multiple_threads attribute_hidden;
> +int __libc_multiple_threads __attribute__ ((nocommon));
> +libc_hidden_data_def (__libc_multiple_threads)
>  # endif
>  #endif
> diff --git a/nptl/libc_pthread_init.c b/nptl/libc_pthread_init.c
> index 397b83beb6..75f5d28ed6 100644
> --- a/nptl/libc_pthread_init.c
> +++ b/nptl/libc_pthread_init.c
> @@ -27,20 +27,9 @@
>  #include <sysdep.h>
>  #include <ldsodefs.h>
>  
> -
> -#ifdef TLS_MULTIPLE_THREADS_IN_TCB
>  void
> -#else
> -extern int __libc_multiple_threads attribute_hidden;
> -
> -int *
> -#endif
>  __libc_pthread_init (void (*reclaim) (void))
>  {
>    /* Called by a child after fork.  */
>    __register_atfork (NULL, NULL, reclaim, NULL);
> -
> -#ifndef TLS_MULTIPLE_THREADS_IN_TCB
> -  return &__libc_multiple_threads;
> -#endif
>  }
> diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
> index 2724770533..2fb1117f3e 100644
> --- a/nptl/nptl-init.c
> +++ b/nptl/nptl-init.c
> @@ -37,11 +37,6 @@
>  #include <libc-pointer-arith.h>
>  #include <pthread_mutex_conf.h>
>  
> -#ifndef TLS_MULTIPLE_THREADS_IN_TCB
> -/* Pointer to the corresponding variable in libc.  */
> -int *__libc_multiple_threads_ptr attribute_hidden;
> -#endif
> -
>  /* Size and alignment of static TLS block.  */
>  size_t __static_tls_size;
>  size_t __static_tls_align_m1;
> @@ -183,10 +178,7 @@ __pthread_initialize_minimal_internal (void)
>  #endif
>  
>    /* Register the fork generation counter with the libc.  */
> -#ifndef TLS_MULTIPLE_THREADS_IN_TCB
> -  __libc_multiple_threads_ptr =
> -#endif
> -    __libc_pthread_init (__reclaim_stacks);
> +  __libc_pthread_init (__reclaim_stacks);
>  }
>  strong_alias (__pthread_initialize_minimal_internal,
>  	      __pthread_initialize_minimal)
> diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
> index 6b52ca158e..dd6d6c6342 100644
> --- a/nptl/pthreadP.h
> +++ b/nptl/pthreadP.h
> @@ -368,17 +368,13 @@ extern unsigned long int __fork_generation attribute_hidden;
>  extern unsigned long int *__fork_generation_pointer attribute_hidden;
>  
>  /* Register the generation counter in the libpthread with the libc.  */
> -#ifdef TLS_MULTIPLE_THREADS_IN_TCB
>  extern void __libc_pthread_init (void (*reclaim) (void));
> -#else
> -extern int *__libc_pthread_init (void (*reclaim) (void));
>  
> +#ifndef TLS_MULTIPLE_THREADS_IN_TCB
>  /* Variable set to a nonzero value either if more than one thread runs or ran,
>     or if a single-threaded process is trying to cancel itself.  See
>     nptl/descr.h for more context on the single-threaded process case.  */
>  extern int __pthread_multiple_threads attribute_hidden;
> -/* Pointer to the corresponding variable in libc.  */
> -extern int *__libc_multiple_threads_ptr attribute_hidden;
>  #endif
>  
>  extern size_t __pthread_get_minstack (const pthread_attr_t *attr);
> diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
> index 060484cdc8..2cab8f0a34 100644
> --- a/nptl/pthread_cancel.c
> +++ b/nptl/pthread_cancel.c
> @@ -90,7 +90,7 @@ __pthread_cancel (pthread_t th)
>  	   points get executed.  */
>  	THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
>  #ifndef TLS_MULTIPLE_THREADS_IN_TCB
> -	__pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
> +	__pthread_multiple_threads = __libc_multiple_threads = 1;
>  #endif
>      }
>    /* Mark the thread as canceled.  This has to be done
> diff --git a/sysdeps/unix/sysv/linux/single-thread.h b/sysdeps/unix/sysv/linux/single-thread.h
> index a28aaed04d..841f8c69d5 100644
> --- a/sysdeps/unix/sysv/linux/single-thread.h
> +++ b/sysdeps/unix/sysv/linux/single-thread.h
> @@ -27,9 +27,13 @@
>     The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single thread
>     check to use global variables instead of the pthread_t field.  */
>  
> +#ifndef __ASSEMBLER__
> +extern int __libc_multiple_threads;
> +libc_hidden_proto (__libc_multiple_threads)
> +#endif
> +
>  #ifdef SINGLE_THREAD_BY_GLOBAL
>  # if IS_IN (libc)
> -extern int __libc_multiple_threads;
>  #  define SINGLE_THREAD_P \
>    __glibc_likely (__libc_multiple_threads == 0)
>  # elif IS_IN (libpthread)
>