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a0ddb889da
We were using the Mach system call swtch() earlier. It's possible Apple removed this system call in their recent 12.4 upgrade. We're better off using x86 PAUSE here, since Mach is less public than the UNIX syscalls. See #426
76 lines
3 KiB
ArmAsm
76 lines
3 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/dce.h"
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#include "libc/sysv/consts/nr.h"
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#include "libc/macros.internal.h"
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.privileged
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// Asks kernel to let other threads be scheduled.
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//
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// @return 0 on success, or -1 w/ errno
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sched_yield:
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#if SupportsXnu()
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testb IsXnu()
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jz 1f
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pause
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ret
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#endif
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#if SupportsWindows()
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// Windows Support
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//
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// A value of zero, together with the bAlertable parameter set to
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// FALSE, causes the thread to relinquish the remainder of its time
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// slice to any other thread that is ready to run, if there are no
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// pending user APCs on the calling thread. If there are no other
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// threads ready to run and no user APCs are queued, the function
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// returns immediately, and the thread continues execution.
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// ──Quoth MSDN
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testb IsWindows()
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jz 1f
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push %rbp
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mov %rsp,%rbp
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xor %ecx,%ecx
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xor %edx,%edx
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ntcall __imp_SleepEx
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xor %eax,%eax
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pop %rbp
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ret
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#endif
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#if SupportsSystemv()
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// UNIX Support
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1: mov __NR_sched_yield,%eax
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#if SupportsBsd() && SupportsLinux()
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clc
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#endif
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syscall
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#if SupportsBsd()
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jc systemfive_errno
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#endif
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#if SupportsLinux()
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cmp $-4095,%rax
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jae systemfive_error
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#endif
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#endif
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2: ret
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.endfn sched_yield,globl
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.previous
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