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Re: [PATCH 1/4] Add single-thread.h header

From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
To: libc-alpha at sourceware dot org
Date: Tue, 9 Apr 2019 09:11:32 -0300
Subject: Re: [PATCH 1/4] Add single-thread.h header
References: <20190222192703.18177-1-adhemerval.zanella@linaro.org>
Ping.

On 22/02/2019 16:27, Adhemerval Zanella wrote:
> This patch move the single-thread syscall optimization defintions from
> syscall-cancel.h to new header file single-thread.h and also move the
> cancellation definitions from pthreadP.h to syscall-cancel.h.
> 
> The idea is just simplify the inclusion of both syscall-cancel.h and
> single-thread.h (without the requirement of including all pthreadP.h
> defintions).
> 
> No semantic changes expected, checked on a build for all major ABIs.
> 
> 	* nptl/pthreadP.h (CANCEL_ASYNC, CANCEL_RESET, LIBC_CANCEL_ASYNC,
> 	LIBC_CANCEL_RESET, __libc_enable_asynccancel,
> 	__libc_disable_asynccancel, __librt_enable_asynccancel,
> 	__libc_disable_asynccancel, __librt_enable_asynccancel,
> 	__librt_disable_asynccancel): Move to ...
> 	* sysdeps/unix/sysv/linux/sysdep-cancel.h: ... here.
> 	(SINGLE_THREAD_P, RTLD_SINGLE_THREAD_P): Move to ...
> 	* sysdeps/unix/sysv/linux/single-thread.h: ... here.
> 	* sysdeps/generic/single-thread.h: New file.
> 	* sysdeps/unix/sysdep.h: Include single-thread.h.
> 	* sysdeps/unix/sysv/linux/futex-internal.h: Include sysdep-cancel.h.
> 	* sysdeps/unix/sysv/linux/lowlevellock-futex.h: Likewise.
> ---
>  nptl/pthreadP.h                              | 37 ---------
>  sysdeps/generic/single-thread.h              | 24 ++++++
>  sysdeps/unix/sysdep.h                        |  2 +-
>  sysdeps/unix/sysv/linux/futex-internal.h     |  2 +-
>  sysdeps/unix/sysv/linux/lowlevellock-futex.h |  2 +-
>  sysdeps/unix/sysv/linux/single-thread.h      | 64 ++++++++++++++++
>  sysdeps/unix/sysv/linux/sysdep-cancel.h      | 81 ++++++++++----------
>  7 files changed, 133 insertions(+), 79 deletions(-)
>  create mode 100644 sysdeps/generic/single-thread.h
>  create mode 100644 sysdeps/unix/sysv/linux/single-thread.h
> 
> diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
> index 626bd4b096..0beacd1266 100644
> --- a/nptl/pthreadP.h
> +++ b/nptl/pthreadP.h
> @@ -311,34 +311,6 @@ __do_cancel (void)
>  }
>  
>  
> -/* Set cancellation mode to asynchronous.  */
> -#define CANCEL_ASYNC() \
> -  __pthread_enable_asynccancel ()
> -/* Reset to previous cancellation mode.  */
> -#define CANCEL_RESET(oldtype) \
> -  __pthread_disable_asynccancel (oldtype)
> -
> -#if IS_IN (libc)
> -/* Same as CANCEL_ASYNC, but for use in libc.so.  */
> -# define LIBC_CANCEL_ASYNC() \
> -  __libc_enable_asynccancel ()
> -/* Same as CANCEL_RESET, but for use in libc.so.  */
> -# define LIBC_CANCEL_RESET(oldtype) \
> -  __libc_disable_asynccancel (oldtype)
> -#elif IS_IN (libpthread)
> -# define LIBC_CANCEL_ASYNC() CANCEL_ASYNC ()
> -# define LIBC_CANCEL_RESET(val) CANCEL_RESET (val)
> -#elif IS_IN (librt)
> -# define LIBC_CANCEL_ASYNC() \
> -  __librt_enable_asynccancel ()
> -# define LIBC_CANCEL_RESET(val) \
> -  __librt_disable_asynccancel (val)
> -#else
> -# define LIBC_CANCEL_ASYNC()	0 /* Just a dummy value.  */
> -# define LIBC_CANCEL_RESET(val)	((void)(val)) /* Nothing, but evaluate it.  */
> -#endif
> -
> -
>  /* Internal prototypes.  */
>  
>  /* Thread list handling.  */
> @@ -545,15 +517,6 @@ extern int __pthread_cond_wait_2_0 (pthread_cond_2_0_t *cond,
>  extern int __pthread_getaffinity_np (pthread_t th, size_t cpusetsize,
>  				     cpu_set_t *cpuset);
>  
> -/* The two functions are in libc.so and not exported.  */
> -extern int __libc_enable_asynccancel (void) attribute_hidden;
> -extern void __libc_disable_asynccancel (int oldtype) attribute_hidden;
> -
> -
> -/* The two functions are in librt.so and not exported.  */
> -extern int __librt_enable_asynccancel (void) attribute_hidden;
> -extern void __librt_disable_asynccancel (int oldtype) attribute_hidden;
> -
>  #if IS_IN (libpthread)
>  /* Special versions which use non-exported functions.  */
>  extern void __pthread_cleanup_push (struct _pthread_cleanup_buffer *buffer,
> diff --git a/sysdeps/generic/single-thread.h b/sysdeps/generic/single-thread.h
> new file mode 100644
> index 0000000000..0a1520ec49
> --- /dev/null
> +++ b/sysdeps/generic/single-thread.h
> @@ -0,0 +1,24 @@
> +/* Single thread optimization, generic version.
> +   Copyright (C) 2019 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef _SINGLE_THREAD_H
> +#define _SINGLE_THREAD_H
> +
> +#define SINGLE_THREAD_P (0)
> +
> +#endif /* _SINGLE_THREAD_H  */
> diff --git a/sysdeps/unix/sysdep.h b/sysdeps/unix/sysdep.h
> index 7cb6c89825..6e503d7688 100644
> --- a/sysdeps/unix/sysdep.h
> +++ b/sysdeps/unix/sysdep.h
> @@ -16,7 +16,7 @@
>     <http://www.gnu.org/licenses/>.  */
>  
>  #include <sysdeps/generic/sysdep.h>
> -
> +#include <single-thread.h>
>  #include <sys/syscall.h>
>  #define	HAVE_SYSCALLS
>  
> diff --git a/sysdeps/unix/sysv/linux/futex-internal.h b/sysdeps/unix/sysv/linux/futex-internal.h
> index 55f0fab77c..501f993853 100644
> --- a/sysdeps/unix/sysv/linux/futex-internal.h
> +++ b/sysdeps/unix/sysv/linux/futex-internal.h
> @@ -22,7 +22,7 @@
>  #include <sysdeps/nptl/futex-internal.h>
>  #include <errno.h>
>  #include <lowlevellock-futex.h>
> -#include <nptl/pthreadP.h>
> +#include <sysdep-cancel.h>
>  
>  /* See sysdeps/nptl/futex-internal.h for documentation; this file only
>     contains Linux-specific comments.
> diff --git a/sysdeps/unix/sysv/linux/lowlevellock-futex.h b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
> index 6f060b1739..030a14b8dc 100644
> --- a/sysdeps/unix/sysv/linux/lowlevellock-futex.h
> +++ b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
> @@ -21,7 +21,7 @@
>  
>  #ifndef __ASSEMBLER__
>  #include <sysdep.h>
> -#include <tls.h>
> +#include <sysdep-cancel.h>
>  #include <kernel-features.h>
>  #endif
>  
> diff --git a/sysdeps/unix/sysv/linux/single-thread.h b/sysdeps/unix/sysv/linux/single-thread.h
> new file mode 100644
> index 0000000000..8248c5d8b8
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/single-thread.h
> @@ -0,0 +1,64 @@
> +/* Single thread optimization, Linux version.
> +   Copyright (C) 2019 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef _SINGLE_THREAD_H
> +#define _SINGLE_THREAD_H
> +
> +/* The default way to check if the process is single thread is by using the
> +   pthread_t 'multiple_threads' field.  However for some architectures it
> +   is faster to either use an extra field on TCB or global varibles
> +   (the TCB field is also used on x86 for some single-thread atomic
> +   optimizations).
> +
> +   The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single
> +   thread check to use global variables instead of the pthread_t
> +   field.  */
> +
> +#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)
> +extern int __pthread_multiple_threads;
> +#  define SINGLE_THREAD_P \
> +  __glibc_likely (__pthread_multiple_threads == 0)
> +# elif IS_IN (librt)
> +#   define SINGLE_THREAD_P					\
> +  __glibc_likely (THREAD_GETMEM (THREAD_SELF,			\
> +				 header.multiple_threads) == 0)
> +# else
> +/* For rtld, et cetera.  */
> +#  define SINGLE_THREAD_P (1)
> +# endif
> +#else /* SINGLE_THREAD_BY_GLOBAL  */
> +# if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
> +#   define SINGLE_THREAD_P					\
> +  __glibc_likely (THREAD_GETMEM (THREAD_SELF,			\
> +				 header.multiple_threads) == 0)
> +# else
> +/* For rtld, et cetera.  */
> +#  define SINGLE_THREAD_P (1)
> +# endif
> +#endif /* SINGLE_THREAD_BY_GLOBAL  */
> +
> +#define RTLD_SINGLE_THREAD_P \
> +  __glibc_likely (THREAD_GETMEM (THREAD_SELF, \
> +				 header.multiple_threads) == 0)
> +
> +#endif /* _SINGLE_THREAD_H  */
> diff --git a/sysdeps/unix/sysv/linux/sysdep-cancel.h b/sysdeps/unix/sysv/linux/sysdep-cancel.h
> index 896549c7f7..a831b30106 100644
> --- a/sysdeps/unix/sysv/linux/sysdep-cancel.h
> +++ b/sysdeps/unix/sysv/linux/sysdep-cancel.h
> @@ -17,48 +17,51 @@
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
>  
> +#ifndef _SYSDEP_CANCEL_H
> +#define _SYSDEP_CANCEL_H
> +
>  #include <sysdep.h>
>  #include <tls.h>
> -#include <nptl/pthreadP.h>
> +#include <errno.h>
> +
> +/* The two functions are in libc.so and not exported.  */
> +extern int __libc_enable_asynccancel (void) attribute_hidden;
> +extern void __libc_disable_asynccancel (int oldtype) attribute_hidden;
> +
> +/* The two functions are in librt.so and not exported.  */
> +extern int __librt_enable_asynccancel (void) attribute_hidden;
> +extern void __librt_disable_asynccancel (int oldtype) attribute_hidden;
> +
> +/* The two functions are in libpthread.so and not exported.  */
> +extern int __pthread_enable_asynccancel (void) attribute_hidden;
> +extern void __pthread_disable_asynccancel (int oldtype) attribute_hidden;
>  
> -/* The default way to check if the process is single thread is by using the
> -   pthread_t 'multiple_threads' field.  However for some architectures it
> -   is faster to either use an extra field on TCB or global varibles
> -   (the TCB field is also used on x86 for some single-thread atomic
> -   optimizations).
> +/* Set cancellation mode to asynchronous.  */
> +#define CANCEL_ASYNC() \
> +  __pthread_enable_asynccancel ()
> +/* Reset to previous cancellation mode.  */
> +#define CANCEL_RESET(oldtype) \
> +  __pthread_disable_asynccancel (oldtype)
>  
> -   The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single
> -   thread check to use global variables instead of the pthread_t
> -   field.  */
> +#if IS_IN (libc)
> +/* Same as CANCEL_ASYNC, but for use in libc.so.  */
> +# define LIBC_CANCEL_ASYNC() \
> +  __libc_enable_asynccancel ()
> +/* Same as CANCEL_RESET, but for use in libc.so.  */
> +# define LIBC_CANCEL_RESET(oldtype) \
> +  __libc_disable_asynccancel (oldtype)
> +#elif IS_IN (libpthread)
> +# define LIBC_CANCEL_ASYNC() CANCEL_ASYNC ()
> +# define LIBC_CANCEL_RESET(val) CANCEL_RESET (val)
> +#elif IS_IN (librt)
> +# define LIBC_CANCEL_ASYNC() \
> +  __librt_enable_asynccancel ()
> +# define LIBC_CANCEL_RESET(val) \
> +  __librt_disable_asynccancel (val)
> +#else
> +# define LIBC_CANCEL_ASYNC()	0 /* Just a dummy value.  */
> +# define LIBC_CANCEL_RESET(val)	((void)(val)) /* Nothing, but evaluate it.  */
> +#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)
> -extern int __pthread_multiple_threads;
> -#  define SINGLE_THREAD_P \
> -  __glibc_likely (__pthread_multiple_threads == 0)
> -# elif IS_IN (librt)
> -#   define SINGLE_THREAD_P					\
> -  __glibc_likely (THREAD_GETMEM (THREAD_SELF,			\
> -				 header.multiple_threads) == 0)
> -# else
> -/* For rtld, et cetera.  */
> -#  define SINGLE_THREAD_P (1)
> -# endif
> -#else /* SINGLE_THREAD_BY_GLOBAL  */
> -# if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
> -#   define SINGLE_THREAD_P					\
> -  __glibc_likely (THREAD_GETMEM (THREAD_SELF,			\
> -				 header.multiple_threads) == 0)
> -# else
> -/* For rtld, et cetera.  */
> -#  define SINGLE_THREAD_P (1)
> -# endif
> -#endif /* SINGLE_THREAD_BY_GLOBAL  */
>  
> -#define RTLD_SINGLE_THREAD_P \
> -  __glibc_likely (THREAD_GETMEM (THREAD_SELF, \
> -				 header.multiple_threads) == 0)
> +#endif
>
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