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7a76f21867
Originally, nptl/descr.h included <sys/rseq.h>, but we removed that in commit2c6b4b272e("nptl: Unconditionally use a 32-byte rseq area"). After that, it was not ensured that the RSEQ_SIG macro was defined during sched_getcpu.c compilation that provided a definition. This commit always checks the rseq area for CPU number information before using the other approaches. This adds an unnecessary (but well-predictable) branch on architectures which do not define RSEQ_SIG, but its cost is small compared to the system call. Most architectures that have vDSO acceleration for getcpu also have rseq support. Fixes:2c6b4b272eFixes:1d350aa060Reviewed-by: Arjun Shankar <arjun@redhat.com>
42 lines
1.3 KiB
C
42 lines
1.3 KiB
C
/* Copyright (C) 2007-2024 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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#include <errno.h>
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#include <sched.h>
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#include <sysdep.h>
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#include <sysdep-vdso.h>
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static int
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vsyscall_sched_getcpu (void)
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{
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unsigned int cpu;
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int r = -1;
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#ifdef HAVE_GETCPU_VSYSCALL
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r = INLINE_VSYSCALL (getcpu, 3, &cpu, NULL, NULL);
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#else
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r = INLINE_SYSCALL_CALL (getcpu, &cpu, NULL, NULL);
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#endif
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return r == -1 ? r : cpu;
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}
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int
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sched_getcpu (void)
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{
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int cpu_id = THREAD_GETMEM_VOLATILE (THREAD_SELF, rseq_area.cpu_id);
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return __glibc_likely (cpu_id >= 0) ? cpu_id : vsyscall_sched_getcpu ();
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}
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