64ac24e738
Semaphores are no longer performance-critical, so a generic C implementation is better for maintainability, debuggability and extensibility. Thanks to Peter Zijlstra for fixing the lockdep warning. Thanks to Harvey Harrison for pointing out that the unlikely() was unnecessary. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu>
137 lines
2.8 KiB
ArmAsm
137 lines
2.8 KiB
ArmAsm
/*
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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 <bcrl@kvack.org>
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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 simple
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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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push %ecx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET ecx,0
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push %edx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET edx,0
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call rwsem_down_read_failed
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pop %edx
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CFI_ADJUST_CFA_OFFSET -4
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pop %ecx
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CFI_ADJUST_CFA_OFFSET -4
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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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push %ecx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET ecx,0
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calll rwsem_down_write_failed
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pop %ecx
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CFI_ADJUST_CFA_OFFSET -4
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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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push %ecx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET ecx,0
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call rwsem_wake
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pop %ecx
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CFI_ADJUST_CFA_OFFSET -4
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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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push %ecx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET ecx,0
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push %edx
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CFI_ADJUST_CFA_OFFSET 4
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CFI_REL_OFFSET edx,0
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call rwsem_downgrade_wake
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pop %edx
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CFI_ADJUST_CFA_OFFSET -4
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pop %ecx
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CFI_ADJUST_CFA_OFFSET -4
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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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