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glibc/nptl/sem_init.c
H.J. Lu 3dd2cbfa35 Use 64-bit atomic on sem_t with 8-byte alignment [BZ #33632]
commit 7fec8a5de6
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Nov 13 14:26:08 2025 -0300

    Revert __HAVE_64B_ATOMICS configure check

uses 64-bit atomic operations on sem_t if 64-bit atomics are supported.
But sem_t may be aligned to 32-bit on 32-bit architectures.

1. Add a macro, SEM_T_ALIGN, for sem_t alignment.
2. Add a macro, HAVE_UNALIGNED_64B_ATOMICS.  Define it if unaligned 64-bit
atomic operations are supported.
3. Add a macro, USE_64B_ATOMICS_ON_SEM_T.  Define to 1 if 64-bit atomic
operations are supported and SEM_T_ALIGN is at least 8-byte aligned or
HAVE_UNALIGNED_64B_ATOMICS is defined.
4. Assert that size and alignment of sem_t are not lower than those of
the internal struct new_sem.
5. Check USE_64B_ATOMICS_ON_SEM_T, instead of USE_64B_ATOMICS, when using
64-bit atomic operations on sem_t.

This fixes BZ #33632.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>
2025-12-02 06:50:49 +08:00

87 lines
2.4 KiB
C

/* Copyright (C) 2002-2025 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/>. */
#include <errno.h>
#include <semaphore.h>
#include <shlib-compat.h>
#include "semaphoreP.h"
#include <kernel-features.h>
int
__new_sem_init (sem_t *sem, int pshared, unsigned int value)
{
ASSERT_PTHREAD_INTERNAL_SIZE (sem_t, struct new_sem);
/* Parameter sanity check. */
if (__glibc_unlikely (value > SEM_VALUE_MAX))
{
__set_errno (EINVAL);
return -1;
}
/* Map to the internal type. */
struct new_sem *isem = (struct new_sem *) sem;
/* Use the values the caller provided. */
#if USE_64B_ATOMICS_ON_SEM_T
isem->data = value;
#else
isem->value = value << SEM_VALUE_SHIFT;
/* pad is used as a mutex on pre-v9 sparc and ignored otherwise. */
isem->pad = 0;
isem->nwaiters = 0;
#endif
isem->private = (pshared == 0 ? FUTEX_PRIVATE : FUTEX_SHARED);
return 0;
}
versioned_symbol (libc, __new_sem_init, sem_init, GLIBC_2_34);
#if OTHER_SHLIB_COMPAT(libpthread, GLIBC_2_1, GLIBC_2_34)
compat_symbol (libpthread, __new_sem_init, sem_init, GLIBC_2_1);
#endif
#if OTHER_SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_1)
int
attribute_compat_text_section
__old_sem_init (sem_t *sem, int pshared, unsigned int value)
{
ASSERT_PTHREAD_INTERNAL_SIZE (sem_t, struct new_sem);
/* Parameter sanity check. */
if (__glibc_unlikely (value > SEM_VALUE_MAX))
{
__set_errno (EINVAL);
return -1;
}
/* Map to the internal type. */
struct old_sem *isem = (struct old_sem *) sem;
/* Use the value the user provided. */
isem->value = value;
/* We cannot store the PSHARED attribute. So we always use the
operations needed for shared semaphores. */
return 0;
}
compat_symbol (libpthread, __old_sem_init, sem_init, GLIBC_2_0);
#endif