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elf: Add CPU iteration support for future use in ld.so diagnostics
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
This commit is contained in:
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elf/dl-iterate_cpu.h
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136
elf/dl-iterate_cpu.h
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/* Iterate over all CPUs, for CPU-specific diagnostics.
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Copyright (C) 2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef DL_ITERATE_CPU_H
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#define DL_ITERATE_CPU_H
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#include <dl-affinity.h>
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#include <stdbool.h>
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struct dl_iterate_cpu
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{
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/* Sequential iteration count, starting at 0. */
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unsigned int processor_index;
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/* Requested CPU. Can be -1 if affinity could not be set. */
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int requested_cpu;
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/* Observed current CPU. -1 if unavailable. */
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int actual_cpu;
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/* Observed node ID for the CPU. -1 if unavailable. */
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int actual_node;
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/* Internal fields to implement the iteration. */
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/* Affinity as obtained by _dl_iterate_cpu_init, using
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_dl_getaffinity. Space for 8,192 CPUs. */
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unsigned long int mask_reference[8192 / sizeof (unsigned long int) / 8];
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/* This array is used by _dl_setaffinity calls. */
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unsigned long int mask_request[8192 / sizeof (unsigned long int) / 8];
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/* Return value from the initial _dl_getaffinity call. */
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int length_reference;
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};
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static void
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_dl_iterate_cpu_init (struct dl_iterate_cpu *dic)
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{
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dic->length_reference
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= _dl_getaffinity (dic->mask_reference, sizeof (dic->mask_reference));
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/* Prepare for the first _dl_iterate_cpu_next call. */
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dic->processor_index = -1;
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dic->requested_cpu = -1;
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}
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static bool
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_dl_iterate_cpu_next (struct dl_iterate_cpu *dic)
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{
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++dic->processor_index;
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if (dic->length_reference > 0)
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{
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/* Search for the next CPU to switch to. */
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while (true)
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{
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++dic->requested_cpu;
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/* Array index and bit number within the array. */
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unsigned int long_index
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= dic->requested_cpu / sizeof (unsigned long int) / 8;
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unsigned int bit_index
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= dic->requested_cpu % (sizeof (unsigned long int) * 8);
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if (long_index * sizeof (unsigned long int) >= dic->length_reference)
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/* All possible CPUs have been covered. */
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return false;
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unsigned long int bit = 1UL << bit_index;
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if (dic->mask_reference[long_index] & bit)
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{
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/* The CPU is available. Try to select it. */
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dic->mask_request[long_index] = bit;
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if (_dl_setaffinity (dic->mask_request,
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(long_index + 1)
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* sizeof (unsigned long int)) < 0)
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{
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/* Record that we could not perform a CPU request. */
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dic->length_reference = -1;
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if (dic->processor_index > 0)
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/* We already reported something. There is no need to
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continue because the new data is probably not useful. */
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return false;
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}
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/* Clear the bit in case the next iteration switches to the
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next long value. */
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dic->mask_request[long_index] = 0;
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/* We found a CPU to run on. */
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break;
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}
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}
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}
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else
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{
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/* No way to set CPU affinity. Iterate just once. */
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if (dic->processor_index > 0)
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return false;
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}
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/* Fill in the actual CPU information. CPU pinning may not actually
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be effective, depending on the container host. */
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unsigned int cpu, node;
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if (_dl_getcpu (&cpu, &node) < 0)
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{
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/* No CPU information available. */
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dic->actual_cpu = -1;
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dic->actual_node = -1;
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}
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else
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{
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dic->actual_cpu = cpu;
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dic->actual_node = node;
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}
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return true;
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}
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#endif /* DL_ITERATE_CPU_H */
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54
sysdeps/generic/dl-affinity.h
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54
sysdeps/generic/dl-affinity.h
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/* CPU affinity handling for the dynamic linker. Stub version.
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Copyright (C) 2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef DL_AFFINITY_H
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#define DL_AFFINITY_H
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#include <errno.h>
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#include <stddef.h>
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/* On success, write the current CPU ID to *CPU, and the current node
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ID to *NODE, and return 0. Return a negative error code on
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failure. */
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static inline int
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_dl_getcpu (unsigned int *cpu, unsigned int *node)
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{
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return -ENOSYS;
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}
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/* On success, write CPU ID affinity bits for the current thread to
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*BITS, which must be SIZE bytes long, and return the number of
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bytes updated, a multiple of sizeof (unsigned long int). On
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failure, return a negative error code. */
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static int
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_dl_getaffinity (unsigned long int *bits, size_t size)
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{
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return -ENOSYS;
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}
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/* Set the CPU affinity mask for the current thread to *BITS, using
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the SIZE bytes from that array, which should be a multiple of
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sizeof (unsigned long int). Return 0 on success, and a negative
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error code on failure. */
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static int
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_dl_setaffinity (const unsigned long int *bits, size_t size)
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{
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return -ENOSYS;
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}
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#endif /* DL_AFFINITY_H */
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46
sysdeps/unix/sysv/linux/dl-affinity.h
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46
sysdeps/unix/sysv/linux/dl-affinity.h
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/* CPU affinity handling for the dynamic linker. Linux version.
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Copyright (C) 2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* See sysdeps/generic/dl-affinity.h for documentation of these interfaces. */
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#ifndef DL_AFFINITY_H
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#define DL_AFFINITY_H
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#include <sysdep.h>
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#include <stddef.h>
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#include <unistd.h>
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static inline int
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_dl_getcpu (unsigned int *cpu, unsigned int *node)
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{
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return INTERNAL_SYSCALL_CALL (getcpu, cpu, node);
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}
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static int
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_dl_getaffinity (unsigned long int *bits, size_t size)
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{
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return INTERNAL_SYSCALL_CALL (sched_getaffinity, /* TID */ 0, size, bits);
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}
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static int
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_dl_setaffinity (const unsigned long int *bits, size_t size)
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{
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return INTERNAL_SYSCALL_CALL (sched_setaffinity, /* TID */ 0, size, bits);
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}
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#endif /* DL_AFFINITY_H */
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