263 lines
8.5 KiB
Diff
263 lines
8.5 KiB
Diff
commit 5653ccd847f0cd3a98906e44c97c71d68652d326
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Mon Apr 8 16:48:55 2024 +0200
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elf: Add CPU iteration support for future use in ld.so diagnostics
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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diff --git a/elf/dl-iterate_cpu.h b/elf/dl-iterate_cpu.h
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new file mode 100644
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index 0000000000..60db167b13
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--- /dev/null
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+++ b/elf/dl-iterate_cpu.h
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@@ -0,0 +1,136 @@
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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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+
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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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+
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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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+
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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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+
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+#ifndef DL_ITERATE_CPU_H
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+#define DL_ITERATE_CPU_H
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+
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+#include <dl-affinity.h>
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+#include <stdbool.h>
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+
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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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+
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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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+
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+ /* Observed current CPU. -1 if unavailable. */
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+ int actual_cpu;
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+
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+ /* Observed node ID for the CPU. -1 if unavailable. */
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+ int actual_node;
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+
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+ /* Internal fields to implement the iteration. */
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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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+ return true;
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+}
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+
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+#endif /* DL_ITERATE_CPU_H */
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diff --git a/sysdeps/generic/dl-affinity.h b/sysdeps/generic/dl-affinity.h
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new file mode 100644
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index 0000000000..d117f737e9
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--- /dev/null
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+++ b/sysdeps/generic/dl-affinity.h
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@@ -0,0 +1,54 @@
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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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+
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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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+
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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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+
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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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+
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+#ifndef DL_AFFINITY_H
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+#define DL_AFFINITY_H
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+
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+#include <errno.h>
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+#include <stddef.h>
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+
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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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+
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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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+
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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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+
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+#endif /* DL_AFFINITY_H */
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diff --git a/sysdeps/unix/sysv/linux/dl-affinity.h b/sysdeps/unix/sysv/linux/dl-affinity.h
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new file mode 100644
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index 0000000000..bbfede7750
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--- /dev/null
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+++ b/sysdeps/unix/sysv/linux/dl-affinity.h
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@@ -0,0 +1,46 @@
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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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+
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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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+
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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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+
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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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+
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+/* See sysdeps/generic/dl-affinity.h for documentation of these interfaces. */
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+
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+#ifndef DL_AFFINITY_H
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+#define DL_AFFINITY_H
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+
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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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+
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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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+
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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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+
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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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+
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+#endif /* DL_AFFINITY_H */
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