[PATCH 03/13] nptl: Export __libc_multiple_threads from libc as an internal symbol
Carlos O'Donell
carlos@redhat.com
Sun May 9 21:42:20 GMT 2021
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)
>
--
Cheers,
Carlos.
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