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208 lines
7.7 KiB
208 lines
7.7 KiB
commit cda99af14e82b4bb6abaecd717ebe3b57c0aa534 |
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Author: Adhemerval Zanella <adhemerval.zanella@linaro.org> |
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Date: Mon Sep 6 12:28:24 2021 -0300 |
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linux: Simplify get_nprocs |
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This patch simplifies the memory allocation code and uses the sched |
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routines instead of reimplement it. This still uses a stack |
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allocation buffer, so it can be used on malloc initialization code. |
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Linux currently supports at maximum of 4096 cpus for most architectures: |
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$ find -iname Kconfig | xargs git grep -A10 -w NR_CPUS | grep -w range |
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arch/alpha/Kconfig- range 2 32 |
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arch/arc/Kconfig- range 2 4096 |
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arch/arm/Kconfig- range 2 16 if DEBUG_KMAP_LOCAL |
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arch/arm/Kconfig- range 2 32 if !DEBUG_KMAP_LOCAL |
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arch/arm64/Kconfig- range 2 4096 |
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arch/csky/Kconfig- range 2 32 |
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arch/hexagon/Kconfig- range 2 6 if SMP |
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arch/ia64/Kconfig- range 2 4096 |
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arch/mips/Kconfig- range 2 256 |
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arch/openrisc/Kconfig- range 2 32 |
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arch/parisc/Kconfig- range 2 32 |
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arch/riscv/Kconfig- range 2 32 |
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arch/s390/Kconfig- range 2 512 |
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arch/sh/Kconfig- range 2 32 |
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arch/sparc/Kconfig- range 2 32 if SPARC32 |
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arch/sparc/Kconfig- range 2 4096 if SPARC64 |
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arch/um/Kconfig- range 1 1 |
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arch/x86/Kconfig-# [NR_CPUS_RANGE_BEGIN ... NR_CPUS_RANGE_END] range. |
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arch/x86/Kconfig- range NR_CPUS_RANGE_BEGIN NR_CPUS_RANGE_END |
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arch/xtensa/Kconfig- range 2 32 |
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With x86 supporting 8192: |
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arch/x86/Kconfig |
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976 config NR_CPUS_RANGE_END |
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977 int |
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978 depends on X86_64 |
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979 default 8192 if SMP && CPUMASK_OFFSTACK |
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980 default 512 if SMP && !CPUMASK_OFFSTACK |
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981 default 1 if !SMP |
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So using a maximum of 32k cpu should cover all cases (and I would |
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expect once we start to have many more CPUs that Linux would provide |
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a more straightforward way to query for such information). |
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A test is added to check if sched_getaffinity can successfully return |
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with large buffers. |
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Checked on x86_64-linux-gnu and i686-linux-gnu. |
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Reviewed-by: Florian Weimer <fweimer@redhat.com> |
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(cherry picked from commit 33099d72e41cf8a129b362e9709eb2be9372d844) |
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diff --git a/posix/Makefile b/posix/Makefile |
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index a5229777eeb0e067..61fcdf015b4ec83b 100644 |
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--- a/posix/Makefile |
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+++ b/posix/Makefile |
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@@ -107,7 +107,8 @@ tests := test-errno tstgetopt testfnm runtests runptests \ |
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tst-sysconf-empty-chroot tst-glob_symlinks tst-fexecve \ |
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tst-glob-tilde test-ssize-max tst-spawn4 bug-regex37 \ |
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bug-regex38 tst-regcomp-truncated tst-spawn-chdir \ |
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- tst-wordexp-nocmd tst-execveat tst-spawn5 |
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+ tst-wordexp-nocmd tst-execveat tst-spawn5 \ |
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+ tst-sched_getaffinity |
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# Test for the glob symbol version that was replaced in glibc 2.27. |
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ifeq ($(have-GLIBC_2.26)$(build-shared),yesyes) |
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diff --git a/posix/tst-sched_getaffinity.c b/posix/tst-sched_getaffinity.c |
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new file mode 100644 |
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index 0000000000000000..db9d517a96fdd99e |
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--- /dev/null |
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+++ b/posix/tst-sched_getaffinity.c |
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@@ -0,0 +1,48 @@ |
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+/* Tests for sched_getaffinity with large buffers. |
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+ Copyright (C) 2021 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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+#include <array_length.h> |
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+#include <sched.h> |
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+#include <support/check.h> |
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+ |
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+/* NB: this test may fail on system with more than 32k cpus. */ |
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+ |
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+static int |
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+do_test (void) |
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+{ |
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+ /* The values are larger than the default cpu_set_t. */ |
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+ const int bufsize[] = { 1<<11, 1<<12, 1<<13, 1<<14, 1<<15, 1<<16, 1<<17 }; |
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+ int cpucount[array_length (bufsize)]; |
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+ |
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+ for (int i = 0; i < array_length (bufsize); i++) |
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+ { |
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+ cpu_set_t *cpuset = CPU_ALLOC (bufsize[i]); |
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+ TEST_VERIFY (cpuset != NULL); |
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+ size_t size = CPU_ALLOC_SIZE (bufsize[i]); |
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+ TEST_COMPARE (sched_getaffinity (0, size, cpuset), 0); |
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+ cpucount[i] = CPU_COUNT_S (size, cpuset); |
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+ CPU_FREE (cpuset); |
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+ } |
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+ |
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+ for (int i = 0; i < array_length (cpucount) - 1; i++) |
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+ TEST_COMPARE (cpucount[i], cpucount[i + 1]); |
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+ |
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+ return 0; |
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+} |
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+ |
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+#include <support/test-driver.c> |
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diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c |
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index 120ce1bb756b09cc..61d20e7bab8640f2 100644 |
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--- a/sysdeps/unix/sysv/linux/getsysstats.c |
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+++ b/sysdeps/unix/sysv/linux/getsysstats.c |
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@@ -29,61 +29,29 @@ |
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#include <sys/sysinfo.h> |
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#include <sysdep.h> |
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-/* Compute the population count of the entire array. */ |
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-static int |
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-__get_nprocs_count (const unsigned long int *array, size_t length) |
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-{ |
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- int count = 0; |
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- for (size_t i = 0; i < length; ++i) |
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- if (__builtin_add_overflow (count, __builtin_popcountl (array[i]), |
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- &count)) |
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- return INT_MAX; |
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- return count; |
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-} |
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- |
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-/* __get_nprocs with a large buffer. */ |
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-static int |
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-__get_nprocs_large (void) |
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-{ |
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- /* This code cannot use scratch_buffer because it is used during |
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- malloc initialization. */ |
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- size_t pagesize = GLRO (dl_pagesize); |
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- unsigned long int *page = __mmap (0, pagesize, PROT_READ | PROT_WRITE, |
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- MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); |
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- if (page == MAP_FAILED) |
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- return 2; |
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- int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, pagesize, page); |
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- int count; |
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- if (r > 0) |
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- count = __get_nprocs_count (page, pagesize / sizeof (unsigned long int)); |
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- else if (r == -EINVAL) |
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- /* One page is still not enough to store the bits. A more-or-less |
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- arbitrary value. This assumes t hat such large systems never |
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- happen in practice. */ |
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- count = GLRO (dl_pagesize) * CHAR_BIT; |
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- else |
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- count = 2; |
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- __munmap (page, GLRO (dl_pagesize)); |
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- return count; |
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-} |
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- |
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int |
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__get_nprocs (void) |
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{ |
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- /* Fast path for most systems. The kernel expects a buffer size |
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- that is a multiple of 8. */ |
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- unsigned long int small_buffer[1024 / CHAR_BIT / sizeof (unsigned long int)]; |
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- int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, |
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- sizeof (small_buffer), small_buffer); |
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+ enum |
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+ { |
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+ max_num_cpus = 32768, |
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+ cpu_bits_size = CPU_ALLOC_SIZE (32768) |
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+ }; |
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+ |
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+ /* This cannot use malloc because it is used on malloc initialization. */ |
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+ __cpu_mask cpu_bits[cpu_bits_size / sizeof (__cpu_mask)]; |
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+ int r = INTERNAL_SYSCALL_CALL (sched_getaffinity, 0, cpu_bits_size, |
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+ cpu_bits); |
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if (r > 0) |
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- return __get_nprocs_count (small_buffer, r / sizeof (unsigned long int)); |
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+ return CPU_COUNT_S (cpu_bits_size, (cpu_set_t*) cpu_bits); |
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else if (r == -EINVAL) |
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- /* The kernel requests a larger buffer to store the data. */ |
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- return __get_nprocs_large (); |
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- else |
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- /* Some other error. 2 is conservative (not a uniprocessor |
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- system, so atomics are needed). */ |
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- return 2; |
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+ /* The input buffer is still not enough to store the number of cpus. This |
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+ is an arbitrary values assuming such systems should be rare and there |
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+ is no offline cpus. */ |
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+ return max_num_cpus; |
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+ /* Some other error. 2 is conservative (not a uniprocessor system, so |
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+ atomics are needed). */ |
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+ return 2; |
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} |
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libc_hidden_def (__get_nprocs) |
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weak_alias (__get_nprocs, get_nprocs)
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