projects / apple / libc.git / blame
| Commit | Line | Data |
|---|---|---|
| 1f2f436a A |
1 | /* |
| 2 | * Copyright (c) 2002 Apple Computer, Inc. All rights reserved. | |
| 3 | * | |
| 4 | * @APPLE_LICENSE_HEADER_START@ | |
| 5 | * | |
| 6 | * This file contains Original Code and/or Modifications of Original Code | |
| 7 | * as defined in and that are subject to the Apple Public Source License | |
| 8 | * Version 2.0 (the 'License'). You may not use this file except in | |
| 9 | * compliance with the License. Please obtain a copy of the License at | |
| 10 | * http://www.opensource.apple.com/apsl/ and read it before using this | |
| 11 | * file. | |
| 12 | * | |
| 13 | * The Original Code and all software distributed under the License are | |
| 14 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER | |
| 15 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, | |
| 16 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, | |
| 17 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. | |
| 18 | * Please see the License for the specific language governing rights and | |
| 19 | * limitations under the License. | |
| 20 | * | |
| 21 | * @APPLE_LICENSE_HEADER_END@ | |
| 22 | */ | |
| 23 | ||
| 24 | #include <machine/cpu_capabilities.h> | |
| 25 | #include <mach/i386/syscall_sw.h> | |
| 26 | ||
| 27 | /* Subroutine to make a preempt syscall. Called when we notice %ebx is | |
| 28 | * nonzero after returning from a PFZ subroutine. Not in PFZ. | |
| 29 | * | |
| 30 | * All registers preserved (but does clear the %ebx preemption flag). | |
| 31 | */ | |
| 32 | .align 2 | |
| 33 | .private_extern _preempt | |
| 34 | _preempt: | |
| 35 | pushq %rax | |
| 36 | pushq %rcx | |
| 37 | pushq %r11 | |
| 38 | movl $(SYSCALL_CONSTRUCT_MACH(58)),%eax /* 58 = pfz_exit */ | |
| 39 | xorl %ebx,%ebx | |
| 40 | syscall | |
| 41 | popq %r11 | |
| 42 | popq %rcx | |
| 43 | popq %rax | |
| 44 | ret | |
| 45 | ||
| 46 | /* Subroutine to back off if we cannot get the spinlock. Called | |
| 47 | * after a few attempts inline in the PFZ subroutines. This code is | |
| 48 | * not in the PFZ. | |
| 49 | * %rdi = ptr to queue head structure | |
| 50 | * %ebx = preemption flag (nonzero if preemption pending) | |
| 51 | * Uses: %rax. | |
| 52 | */ | |
| 53 | .align 2 | |
| 54 | .private_extern _backoff | |
| 55 | _backoff: | |
| 56 | testl %ebx,%ebx // does kernel want to preempt us? | |
| 57 | jz 1f // no | |
| 58 | call _preempt | |
| 59 | 1: | |
| 60 | pause // SMT-friendly backoff | |
| 61 | cmpl $0,16(%rdi) // sniff the lockword | |
| 62 | jnz 1b // loop if still taken | |
| 63 | ret // lockword is free, so reenter PFZ |