[PATCH] nptl: Eliminate <smp.h> and __is_smp
Adhemerval Zanella
adhemerval.zanella@linaro.org
Fri Nov 13 13:45:29 GMT 2020
On 13/11/2020 06:45, Florian Weimer via Libc-alpha wrote:
> Most systems are SMP, so optimizing for the UP case is no longer
> approriate. A dynamic check based on the kernel identification
> has been only implemented for i386 anyway.
>
> To disable adaptive mutexes on sh, define DEFAULT_ADAPTIVE_COUNT
> as zero for this architecture.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
> ---
> nptl/nptl-init.c | 4 --
> nptl/pthreadP.h | 3 --
> nptl/pthread_mutex_lock.c | 3 --
> nptl/pthread_mutex_timedlock.c | 3 --
> nptl/smp.h | 27 ------------
> nptl/vars.c | 3 --
> sysdeps/unix/sysv/linux/i386/smp.h | 55 ------------------------
> sysdeps/unix/sysv/linux/sh/adaptive_spin_count.h | 20 +++++++++
> sysdeps/unix/sysv/linux/sh/smp.h | 23 ----------
> 9 files changed, 20 insertions(+), 121 deletions(-)
>
> diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
> index 95c60a524a..4aa1231bec 100644
> --- a/nptl/nptl-init.c
> +++ b/nptl/nptl-init.c
> @@ -32,7 +32,6 @@
> #include <fork.h>
> #include <version.h>
> #include <shlib-compat.h>
> -#include <smp.h>
> #include <lowlevellock.h>
> #include <futex-internal.h>
> #include <kernel-features.h>
Ok.
> @@ -346,9 +345,6 @@ __pthread_initialize_minimal_internal (void)
> __libc_pthread_init (&__fork_generation, __reclaim_stacks,
> ptr_pthread_functions);
>
> - /* Determine whether the machine is SMP or not. */
> - __is_smp = is_smp_system ();
> -
> #if HAVE_TUNABLES
> __pthread_tunables_init ();
> #endif
Ok.
> diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
> index 710b21e890..686f54aa93 100644
> --- a/nptl/pthreadP.h
> +++ b/nptl/pthreadP.h
> @@ -208,9 +208,6 @@ extern void __default_pthread_attr_freeres (void) attribute_hidden;
> extern size_t __static_tls_size attribute_hidden;
> extern size_t __static_tls_align_m1 attribute_hidden;
>
> -/* Flag whether the machine is SMP or not. */
> -extern int __is_smp attribute_hidden;
> -
> /* Thread descriptor handling. */
> extern list_t __stack_user;
> hidden_proto (__stack_user)
Ok.
> diff --git a/nptl/pthread_mutex_lock.c b/nptl/pthread_mutex_lock.c
> index 7858abd528..fac774e608 100644
> --- a/nptl/pthread_mutex_lock.c
> +++ b/nptl/pthread_mutex_lock.c
> @@ -120,9 +120,6 @@ __pthread_mutex_lock (pthread_mutex_t *mutex)
> else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
> == PTHREAD_MUTEX_ADAPTIVE_NP, 1))
> {
> - if (! __is_smp)
> - goto simple;
> -
> if (LLL_MUTEX_TRYLOCK (mutex) != 0)
> {
> int cnt = 0;
Ok.
> diff --git a/nptl/pthread_mutex_timedlock.c b/nptl/pthread_mutex_timedlock.c
> index fe9e651f6c..de88e9fc25 100644
> --- a/nptl/pthread_mutex_timedlock.c
> +++ b/nptl/pthread_mutex_timedlock.c
> @@ -113,9 +113,6 @@ __pthread_mutex_clocklock_common (pthread_mutex_t *mutex,
>
>
> case PTHREAD_MUTEX_ADAPTIVE_NP:
> - if (! __is_smp)
> - goto simple;
> -
> if (lll_trylock (mutex->__data.__lock) != 0)
> {
> int cnt = 0;
Ok.
> diff --git a/nptl/smp.h b/nptl/smp.h
> deleted file mode 100644
> index 537e5e945c..0000000000
> --- a/nptl/smp.h
> +++ /dev/null
> @@ -1,27 +0,0 @@
> -/* Determine whether the host has multiple processors. Stub version.
> - Copyright (C) 1996-2020 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 Library General Public License as
> - published by the Free Software Foundation; either version 2 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
> - Library General Public License for more details.
> -
> - You should have received a copy of the GNU Library General Public
> - License along with the GNU C Library; see the file COPYING.LIB. If
> - not, see <https://www.gnu.org/licenses/>. */
> -
> -/* Test whether the machine has more than one processor. This is not the
> - best test but good enough. More complicated tests would require `malloc'
> - which is not available at that time. */
> -static inline int
> -is_smp_system (void)
> -{
> - /* Assume all machines are SMP and/or CMT and/or SMT. */
> - return 1;
> -}
Ok.
> diff --git a/nptl/vars.c b/nptl/vars.c
> index 3696020145..2f52391dc2 100644
> --- a/nptl/vars.c
> +++ b/nptl/vars.c
> @@ -27,9 +27,6 @@ union pthread_attr_transparent __default_pthread_attr attribute_hidden;
> /* Mutex protecting __default_pthread_attr. */
> int __default_pthread_attr_lock = LLL_LOCK_INITIALIZER;
>
> -/* Flag whether the machine is SMP or not. */
> -int __is_smp attribute_hidden;
> -
> #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
Ok.
> diff --git a/sysdeps/unix/sysv/linux/i386/smp.h b/sysdeps/unix/sysv/linux/i386/smp.h
> deleted file mode 100644
> index 85a630d048..0000000000
> --- a/sysdeps/unix/sysv/linux/i386/smp.h
> +++ /dev/null
> @@ -1,55 +0,0 @@
> -/* Determine whether the host has multiple processors. Linux version.
> - Copyright (C) 1996-2020 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 Library General Public License as
> - published by the Free Software Foundation; either version 2 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
> - Library General Public License for more details.
> -
> - You should have received a copy of the GNU Library General Public
> - License along with the GNU C Library; see the file COPYING.LIB. If
> - not, see <https://www.gnu.org/licenses/>. */
> -
> -#include <errno.h>
> -#include <fcntl.h>
> -#include <string.h>
> -#include <sys/utsname.h>
> -#include <not-cancel.h>
> -
> -/* Test whether the machine has more than one processor. This is not the
> - best test but good enough. More complicated tests would require `malloc'
> - which is not available at that time. */
> -static inline int
> -is_smp_system (void)
> -{
> - union
> - {
> - struct utsname uts;
> - char buf[512];
> - } u;
> - char *cp;
> -
> - /* Try reading the number using `sysctl' first. */
> - if (__uname (&u.uts) == 0)
> - cp = u.uts.version;
> - else
> - {
> - /* This was not successful. Now try reading the /proc filesystem. */
> - int fd = __open64_nocancel ("/proc/sys/kernel/version", O_RDONLY);
> - if (__builtin_expect (fd, 0) == -1
> - || __read_nocancel (fd, u.buf, sizeof (u.buf)) <= 0)
> - /* This also didn't work. We give up and say it's a UP machine. */
> - u.buf[0] = '\0';
> -
> - __close_nocancel_nostatus (fd);
> - cp = u.buf;
> - }
> -
> - return strstr (cp, "SMP") != NULL;
> -}
Ok.
> diff --git a/sysdeps/unix/sysv/linux/sh/adaptive_spin_count.h b/sysdeps/unix/sysv/linux/sh/adaptive_spin_count.h
> new file mode 100644
> index 0000000000..3431cd3d8c
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/sh/adaptive_spin_count.h
> @@ -0,0 +1,20 @@
> +/* Maximum adaptive spin count default for sh.
> + Copyright (C) 2020 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
> + <https://www.gnu.org/licenses/>. */
> +
> +/* Disable spinning because sh is always uniprocessor. */
> +#define DEFAULT_ADAPTIVE_COUNT 0
Ok. Maybe an option is dropping this optimization in favor a simplified
code base.
> diff --git a/sysdeps/unix/sysv/linux/sh/smp.h b/sysdeps/unix/sysv/linux/sh/smp.h
> deleted file mode 100644
> index 55efedc0ba..0000000000
> --- a/sysdeps/unix/sysv/linux/sh/smp.h
> +++ /dev/null
> @@ -1,23 +0,0 @@
> -/* Determine whether the host has multiple processors. SH version.
> - Copyright (C) 2002-2020 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 Library General Public License as
> - published by the Free Software Foundation; either version 2 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
> - Library General Public License for more details.
> -
> - You should have received a copy of the GNU Library General Public
> - License along with the GNU C Library; see the file COPYING.LIB. If
> - not, see <https://www.gnu.org/licenses/>. */
> -
> -static inline int
> -is_smp_system (void)
> -{
> - return 0;
> -}
>
Ok.
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