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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/x86/lib/semaphore_32.S
10818 views
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/*

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 * i386 semaphore implementation.

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 *

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 * (C) Copyright 1999 Linus Torvalds

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 *

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 * Portions Copyright 1999 Red Hat, Inc.

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 *

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 *	This program is free software; you can redistribute it and/or

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 *	modify it under the terms of the GNU General Public License

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 *	as published by the Free Software Foundation; either version

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 *	2 of the License, or (at your option) any later version.

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 *

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 * rw semaphores implemented November 1999 by Benjamin LaHaise <[email protected]>

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 */

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#include <linux/linkage.h>

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#include <asm/rwlock.h>

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#include <asm/alternative-asm.h>

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#include <asm/frame.h>

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#include <asm/dwarf2.h>

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/*

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 * The semaphore operations have a special calling sequence that

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 * allow us to do a simpler in-line version of them. These routines

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 * need to convert that sequence back into the C sequence when

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 * there is contention on the semaphore.

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 *

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 * %eax contains the semaphore pointer on entry. Save the C-clobbered

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 * registers (%eax, %edx and %ecx) except %eax whish is either a return

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 * value or just clobbered..

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 */

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	.section .sched.text, "ax"

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/*

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 * rw spinlock fallbacks

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 */

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#ifdef CONFIG_SMP

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ENTRY(__write_lock_failed)

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	CFI_STARTPROC

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	FRAME

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2: 	LOCK_PREFIX

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	addl	$ RW_LOCK_BIAS,(%eax)

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1:	rep; nop

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	cmpl	$ RW_LOCK_BIAS,(%eax)

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	jne	1b

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	LOCK_PREFIX

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	subl	$ RW_LOCK_BIAS,(%eax)

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	jnz	2b

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	ENDFRAME

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	ret

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	CFI_ENDPROC

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	ENDPROC(__write_lock_failed)

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ENTRY(__read_lock_failed)

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	CFI_STARTPROC

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	FRAME

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2: 	LOCK_PREFIX

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	incl	(%eax)

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1:	rep; nop

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	cmpl	$1,(%eax)

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	js	1b

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	LOCK_PREFIX

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	decl	(%eax)

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	js	2b

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	ENDFRAME

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	ret

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	CFI_ENDPROC

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	ENDPROC(__read_lock_failed)

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#endif

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#ifdef CONFIG_RWSEM_XCHGADD_ALGORITHM

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/* Fix up special calling conventions */

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ENTRY(call_rwsem_down_read_failed)

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	CFI_STARTPROC

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	pushl_cfi %ecx

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	CFI_REL_OFFSET ecx,0

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	pushl_cfi %edx

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	CFI_REL_OFFSET edx,0

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	call rwsem_down_read_failed

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	popl_cfi %edx

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	popl_cfi %ecx

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	ret

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	CFI_ENDPROC

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	ENDPROC(call_rwsem_down_read_failed)

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ENTRY(call_rwsem_down_write_failed)

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	CFI_STARTPROC

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	pushl_cfi %ecx

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	CFI_REL_OFFSET ecx,0

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	calll rwsem_down_write_failed

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	popl_cfi %ecx

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	ret

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	CFI_ENDPROC

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	ENDPROC(call_rwsem_down_write_failed)

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ENTRY(call_rwsem_wake)

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	CFI_STARTPROC

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	decw %dx    /* do nothing if still outstanding active readers */

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	jnz 1f

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	pushl_cfi %ecx

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	CFI_REL_OFFSET ecx,0

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	call rwsem_wake

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	popl_cfi %ecx

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1:	ret

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	CFI_ENDPROC

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	ENDPROC(call_rwsem_wake)

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/* Fix up special calling conventions */

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ENTRY(call_rwsem_downgrade_wake)

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	CFI_STARTPROC

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	pushl_cfi %ecx

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	CFI_REL_OFFSET ecx,0

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	pushl_cfi %edx

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	CFI_REL_OFFSET edx,0

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	call rwsem_downgrade_wake

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	popl_cfi %edx

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	popl_cfi %ecx

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	ret

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	CFI_ENDPROC

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	ENDPROC(call_rwsem_downgrade_wake)

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#endif

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