projects / apple / libplatform.git / blame
| Commit | Line | Data |
|---|---|---|
| ada7c492 A |
1 | /* |
| 2 | * Copyright (c) 2006-2013 Apple, 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 <architecture/i386/asm_help.h> | |
| 26 | ||
| 27 | .text | |
| 28 | ||
| 29 | /* Subroutine to make a preempt syscall. Called when we notice %ebx is | |
| 30 | * nonzero after returning from a PFZ subroutine. | |
| 31 | * When we enter kernel: | |
| 32 | * %edx = return address | |
| 33 | * %ecx = stack ptr | |
| 34 | * Destroys %eax, %ecx, and %edx. | |
| 35 | */ | |
| 36 | .align 4 | |
| 37 | .private_extern _preempt | |
| 38 | .globl _preempt | |
| 39 | _preempt: | |
| 40 | popl %edx // get return address | |
| 41 | movl %esp,%ecx // save stack ptr here | |
| 42 | movl $(-58),%eax /* 58 = pfz_exit */ | |
| 43 | xorl %ebx,%ebx // clear "preemption pending" flag | |
| 44 | sysenter | |
| 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 | * %edi = ptr to queue head structure | |
| 50 | * %ebx = preemption flag (nonzero if preemption pending) | |
| 51 | * Destroys %eax. | |
| 52 | */ | |
| 53 | ||
| 54 | .align 4 | |
| 55 | .private_extern _backoff | |
| 56 | .globl _backoff | |
| 57 | _backoff: | |
| 58 | testl %ebx,%ebx // does kernel want to preempt us? | |
| 59 | jz 1f // no | |
| 60 | xorl %ebx,%ebx // yes, clear flag | |
| 61 | pushl %edx // preserve regs used by preempt syscall | |
| 62 | pushl %ecx | |
| 63 | call _preempt | |
| 64 | popl %ecx | |
| 65 | popl %edx | |
| 66 | 1: | |
| 67 | pause // SMT-friendly backoff | |
| 68 | cmpl $0,8(%edi) // sniff the lockword | |
| 69 | jnz 1b // loop if still taken | |
| 70 | ret // lockword is free, so reenter PFZ |