From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Florian Weimer <fweimer@redhat.com>, libc-alpha@sourceware.org
Subject: Re: [PATCH v3 33/37] x86: Remove low-level lock optimization
Date: Thu, 25 Mar 2021 17:30:19 -0300 [thread overview]
Message-ID: <708a2fee-a893-0e05-6f83-8c91e45ef071@linaro.org> (raw)
In-Reply-To: <64789336c8a39f75473821f2e08ef1e7ec41d535.1615914632.git.fweimer@redhat.com>
On 16/03/2021 14:31, Florian Weimer via Libc-alpha wrote:
> The current approach is to do this optimizations at a higher level,
> in generic code, so that single-threaded cases can be specifically
> targeted.
>
> Furthermore, using IS_IN (libc) as a compile-time indicator that
> all locks are private is no longer correct once process-shared lock
> implementations are moved into libc.
>
> The generic <lowlevellock.h> is not compatible with assembler code
> (obviously), so it's necessary to remove two long-unused #includes.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> sysdeps/i386/nptl/pthread_spin_lock.S | 1 -
> sysdeps/unix/sysv/linux/x86/lowlevellock.h | 87 ----------------------
> sysdeps/x86_64/nptl/pthread_spin_lock.S | 1 -
> 3 files changed, 89 deletions(-)
> delete mode 100644 sysdeps/unix/sysv/linux/x86/lowlevellock.h
>
> diff --git a/sysdeps/i386/nptl/pthread_spin_lock.S b/sysdeps/i386/nptl/pthread_spin_lock.S
> index eec157fde7..985b236aae 100644
> --- a/sysdeps/i386/nptl/pthread_spin_lock.S
> +++ b/sysdeps/i386/nptl/pthread_spin_lock.S
> @@ -16,7 +16,6 @@
> <https://www.gnu.org/licenses/>. */
>
> #include <sysdep.h>
> -#include <lowlevellock.h>
>
> ENTRY (pthread_spin_lock)
> mov 4(%esp), %eax
Ok.
> diff --git a/sysdeps/unix/sysv/linux/x86/lowlevellock.h b/sysdeps/unix/sysv/linux/x86/lowlevellock.h
> deleted file mode 100644
> index 7205bcadfd..0000000000
> --- a/sysdeps/unix/sysv/linux/x86/lowlevellock.h
> +++ /dev/null
> @@ -1,87 +0,0 @@
> -/* Low-level lock implementation, x86 version.
> - Copyright (C) 2019-2021 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/>. */
> -
> -#ifndef _X86_64_LOWLEVELLOCK_H
> -#define _X86_64_LOWLEVELLOCK_H 1
> -
> -#ifndef __ASSEMBLER__
> -#include <sysdeps/nptl/lowlevellock.h>
> -#include <single-thread.h>
> -
> -/* The lll_trylock, lll_lock, and lll_unlock implements a single-thread
> - optimization using the cmpxchgl instruction. It checks if the process
> - is single thread and avoid a more expensive atomic instruction. */
> -
> -/* The single-thread optimization only works for libc itself, we need
> - atomicity for libpthread in case of shared futexes. */
> -#if !IS_IN(libc)
> -# define is_single_thread 0
> -#else
> -# define is_single_thread SINGLE_THREAD_P
> -#endif
> -
> -/* In the __lllc_as we simply return the value in %eax after the cmpxchg
> - instruction. In case the operation succeeded this value is zero. In case
> - the operation failed, the cmpxchg instruction has loaded the current value
> - of the memory work which is guaranteed to be nonzero. */
> -static inline int
> -__attribute__ ((always_inline))
> -__lll_cas_lock (int *futex)
> -{
> - int ret;
> - asm volatile ("cmpxchgl %2, %1"
> - : "=a" (ret), "=m" (*futex)
> - : "r" (1), "m" (*futex), "0" (0)
> - : "memory");
> - return ret;
> -}
> -
> -#undef lll_trylock
> -#define lll_trylock(lock) \
> - ({ \
> - int __ret; \
> - if (is_single_thread) \
> - __ret = __lll_cas_lock (&(lock)); \
> - else \
> - __ret = __lll_trylock (&(lock)); \
> - __ret; \
> - })
> -
> -#undef lll_lock
> -#define lll_lock(lock, private) \
> - ((void) \
> - ({ \
> - if (is_single_thread) \
> - __lll_cas_lock (&(lock)); \
> - else \
> - __lll_lock (&(lock), private); \
> - }))
> -
> -#undef lll_unlock
> -#define lll_unlock(lock, private) \
> - ((void) \
> - ({ \
> - if (is_single_thread) \
> - (lock)--; \
> - else \
> - __lll_unlock (&(lock), private); \
> - }))
> -
> -#endif /* !__ASSEMBLER__ */
> -
> -#endif /* lowlevellock.h */
Ok.
> diff --git a/sysdeps/x86_64/nptl/pthread_spin_lock.S b/sysdeps/x86_64/nptl/pthread_spin_lock.S
> index 66cbbc5252..ff5e7525ca 100644
> --- a/sysdeps/x86_64/nptl/pthread_spin_lock.S
> +++ b/sysdeps/x86_64/nptl/pthread_spin_lock.S
> @@ -15,7 +15,6 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> -#include <lowlevellock.h>
> #include <sysdep.h>
>
> ENTRY(pthread_spin_lock)
>
Ok.
next prev parent reply other threads:[~2021-03-25 20:30 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 17:27 [PATCH v3 00/37] libpthread removal: NPTL forwarders are gone Florian Weimer
2021-03-16 17:27 ` [PATCH v3 01/37] nptl: Move pthread_mutex_consistent into libc Florian Weimer
2021-03-17 11:36 ` Adhemerval Zanella
2021-03-16 17:27 ` [PATCH v3 02/37] nptl: Move __pthread_cleanup_routine " Florian Weimer
2021-03-16 17:27 ` [PATCH v3 03/37] nptl: Move legacy unwinding implementation " Florian Weimer
2021-03-16 17:27 ` [PATCH v3 04/37] nptl: Move legacy cancelation handling into libc as compat symbols Florian Weimer
2021-03-16 17:27 ` [PATCH v3 05/37] nptl: Remove longjmp, siglongjmp from libpthread Florian Weimer
2021-03-17 11:38 ` Adhemerval Zanella
2021-03-16 17:28 ` [PATCH v3 06/37] x86: Restore compile-time check for shadow stack pointer in longjmp Florian Weimer
2021-03-16 17:28 ` [PATCH v3 07/37] nptl: Move __pthread_cleanup_upto into libc Florian Weimer
2021-03-16 17:28 ` [PATCH v3 08/37] nptl: Move pthread_once and __pthread_once " Florian Weimer
2021-03-17 13:30 ` Adhemerval Zanella
2021-03-17 13:37 ` Adhemerval Zanella
2021-03-17 14:45 ` Florian Weimer
2021-03-17 16:39 ` Adhemerval Zanella
2021-03-17 16:56 ` Florian Weimer
2021-03-17 17:22 ` Adhemerval Zanella
2021-03-17 17:43 ` Florian Weimer
2021-03-17 19:09 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 09/37] nptl: Move __pthread_unwind_next " Florian Weimer
2021-03-17 19:42 ` Adhemerval Zanella
2021-03-17 19:54 ` Florian Weimer
2021-03-17 20:16 ` Adhemerval Zanella
2021-03-17 20:33 ` Florian Weimer
2021-03-17 20:44 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 10/37] csu: Move calling main out of __libc_start_main_impl Florian Weimer
2021-03-17 20:45 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 11/37] nptl: Move internal __nptl_nthreads variable into libc Florian Weimer
2021-03-18 12:42 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 12/37] nptl_db: Introduce DB_MAIN_ARRAY_VARIABLE Florian Weimer
2021-03-18 12:43 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 13/37] nptl: Move __pthread_keys global variable into libc Florian Weimer
2021-03-18 12:44 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 14/37] nptl: Move __nptl_deallocate_tsd " Florian Weimer
2021-03-18 12:46 ` Adhemerval Zanella
2021-03-18 17:16 ` Florian Weimer
2021-03-18 17:54 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 15/37] nptl: Move pthread_exit " Florian Weimer
2021-03-18 12:49 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 16/37] nptl: Move pthread_setcancelstate " Florian Weimer
2021-03-18 12:52 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 17/37] nptl: Move pthread_setcanceltype " Florian Weimer
2021-03-18 12:53 ` Adhemerval Zanella
2021-03-16 17:29 ` [PATCH v3 18/37] nptl: Invoke the set_robust_list system call directly in fork Florian Weimer
2021-03-18 12:54 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 19/37] dlfcn: Failures after dlmopen should not terminate process [BZ #24772] Florian Weimer
2021-03-19 19:56 ` Adhemerval Zanella
2021-03-27 16:57 ` Florian Weimer
2021-03-16 17:30 ` [PATCH v3 20/37] dlfcn: dlerror needs to call free from the base namespace [BZ #24773] Florian Weimer
2021-03-23 14:47 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 21/37] Remove pthread_key_create-related internals from libc-lock.h Florian Weimer
2021-03-23 16:39 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 22/37] elf: Introduce __tls_init_tp for second-phase TCB initialization Florian Weimer
2021-03-23 18:25 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 23/37] nptl: Move part of TCB initialization from libpthread to __tls_init_tp Florian Weimer
2021-03-24 13:56 ` Adhemerval Zanella
2021-03-27 17:19 ` Florian Weimer
2021-03-16 17:30 ` [PATCH v3 24/37] nptl: Move pthread_key_create, __pthread_key_create into libc Florian Weimer
2021-03-24 14:09 ` Adhemerval Zanella
2021-03-24 14:32 ` Florian Weimer
2021-03-24 14:42 ` Adhemerval Zanella
2021-03-24 15:08 ` Florian Weimer
2021-03-24 15:46 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 25/37] nptl: Move pthread_getspecific, __pthread_getspecific " Florian Weimer
2021-03-24 14:12 ` Adhemerval Zanella
2021-03-24 14:38 ` Florian Weimer
2021-03-24 14:43 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 26/37] nptl: Move pthread_setspecific, __pthread_setspecific " Florian Weimer
2021-03-24 14:26 ` Adhemerval Zanella
2021-03-16 17:30 ` [PATCH v3 27/37] nptl: Move pthread_key_delete " Florian Weimer
2021-03-24 14:45 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 28/37] nptl: Move rwlock functions with forwarders " Florian Weimer
2021-03-25 19:52 ` Adhemerval Zanella
2021-03-27 21:41 ` Florian Weimer
2021-03-16 17:31 ` [PATCH v3 29/37] nptl: Move the internal thread priority protection symbols " Florian Weimer
2021-03-25 20:21 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 30/37] pthread: Introduce __pthread_early_init Florian Weimer
2021-03-25 20:22 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 31/37] nptl: Move internal symbol __mutex_aconf into libc Florian Weimer
2021-03-25 20:24 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 32/37] nptl: pthread_mutex_lock, pthread_mutex_unock single-threaded optimization Florian Weimer
2021-03-26 18:00 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 33/37] x86: Remove low-level lock optimization Florian Weimer
2021-03-25 20:30 ` Adhemerval Zanella [this message]
2021-03-16 17:31 ` [PATCH v3 34/37] nptl: Move core mutex functions into libc Florian Weimer
2021-03-25 20:46 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 35/37] nptl: Move core condition variable " Florian Weimer
2021-03-26 17:14 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 36/37] nptl: Move setxid broadcast implementation " Florian Weimer
2021-03-26 18:15 ` Adhemerval Zanella
2021-04-06 18:41 ` Florian Weimer
2021-04-06 18:54 ` Adhemerval Zanella
2021-04-06 19:23 ` Florian Weimer
2021-04-06 19:40 ` Adhemerval Zanella
2021-03-16 17:31 ` [PATCH v3 37/37] nptl: Remove remnants of the libc/libpthread forwarder interface Florian Weimer
2021-03-26 18:19 ` Adhemerval Zanella
2021-03-18 22:06 ` [PATCH v3 00/37] libpthread removal: NPTL forwarders are gone Florian Weimer
2021-03-26 18:25 ` Adhemerval Zanella
2021-03-31 10:18 ` Florian Weimer
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