9a0b5817ad
Implement SMP alternatives, i.e. switching at runtime between different
code versions for UP and SMP. The code can patch both SMP->UP and UP->SMP.
The UP->SMP case is useful for CPU hotplug.
With CONFIG_CPU_HOTPLUG enabled the code switches to UP at boot time and
when the number of CPUs goes down to 1, and switches to SMP when the number
of CPUs goes up to 2.
Without CONFIG_CPU_HOTPLUG or on non-SMP-capable systems the code is
patched once at boot time (if needed) and the tables are released
afterwards.
The changes in detail:
* The current alternatives bits are moved to a separate file,
the SMP alternatives code is added there.
* The patch adds some new elf sections to the kernel:
.smp_altinstructions
like .altinstructions, also contains a list
of alt_instr structs.
.smp_altinstr_replacement
like .altinstr_replacement, but also has some space to
save original instruction before replaving it.
.smp_locks
list of pointers to lock prefixes which can be nop'ed
out on UP.
The first two are used to replace more complex instruction
sequences such as spinlocks and semaphores. It would be possible
to deal with the lock prefixes with that as well, but by handling
them as special case the table sizes become much smaller.
* The sections are page-aligned and padded up to page size, so they
can be free if they are not needed.
* Splitted the code to release init pages to a separate function and
use it to release the elf sections if they are unused.
Signed-off-by: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
135 lines
2.8 KiB
C
135 lines
2.8 KiB
C
/*
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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/config.h>
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#include <asm/semaphore.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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asm(
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".section .sched.text\n"
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".align 4\n"
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".globl __down_failed\n"
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"__down_failed:\n\t"
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#if defined(CONFIG_FRAME_POINTER)
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"pushl %ebp\n\t"
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"movl %esp,%ebp\n\t"
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#endif
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"pushl %edx\n\t"
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"pushl %ecx\n\t"
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"call __down\n\t"
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"popl %ecx\n\t"
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"popl %edx\n\t"
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#if defined(CONFIG_FRAME_POINTER)
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"movl %ebp,%esp\n\t"
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"popl %ebp\n\t"
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#endif
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"ret"
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);
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asm(
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".section .sched.text\n"
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".align 4\n"
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".globl __down_failed_interruptible\n"
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"__down_failed_interruptible:\n\t"
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#if defined(CONFIG_FRAME_POINTER)
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"pushl %ebp\n\t"
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"movl %esp,%ebp\n\t"
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#endif
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"pushl %edx\n\t"
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"pushl %ecx\n\t"
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"call __down_interruptible\n\t"
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"popl %ecx\n\t"
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"popl %edx\n\t"
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#if defined(CONFIG_FRAME_POINTER)
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"movl %ebp,%esp\n\t"
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"popl %ebp\n\t"
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#endif
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"ret"
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);
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asm(
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".section .sched.text\n"
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".align 4\n"
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".globl __down_failed_trylock\n"
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"__down_failed_trylock:\n\t"
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#if defined(CONFIG_FRAME_POINTER)
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"pushl %ebp\n\t"
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"movl %esp,%ebp\n\t"
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#endif
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"pushl %edx\n\t"
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"pushl %ecx\n\t"
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"call __down_trylock\n\t"
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"popl %ecx\n\t"
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"popl %edx\n\t"
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#if defined(CONFIG_FRAME_POINTER)
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"movl %ebp,%esp\n\t"
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"popl %ebp\n\t"
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#endif
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"ret"
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);
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asm(
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".section .sched.text\n"
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".align 4\n"
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".globl __up_wakeup\n"
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"__up_wakeup:\n\t"
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"pushl %edx\n\t"
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"pushl %ecx\n\t"
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"call __up\n\t"
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"popl %ecx\n\t"
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"popl %edx\n\t"
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"ret"
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);
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/*
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* rw spinlock fallbacks
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*/
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#if defined(CONFIG_SMP)
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asm(
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".section .sched.text\n"
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".align 4\n"
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".globl __write_lock_failed\n"
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"__write_lock_failed:\n\t"
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LOCK_PREFIX "addl $" RW_LOCK_BIAS_STR ",(%eax)\n"
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"1: rep; nop\n\t"
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"cmpl $" RW_LOCK_BIAS_STR ",(%eax)\n\t"
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"jne 1b\n\t"
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LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",(%eax)\n\t"
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"jnz __write_lock_failed\n\t"
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"ret"
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);
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asm(
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".section .sched.text\n"
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".align 4\n"
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".globl __read_lock_failed\n"
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"__read_lock_failed:\n\t"
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LOCK_PREFIX "incl (%eax)\n"
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"1: rep; nop\n\t"
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"cmpl $1,(%eax)\n\t"
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"js 1b\n\t"
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LOCK_PREFIX "decl (%eax)\n\t"
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"js __read_lock_failed\n\t"
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"ret"
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);
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#endif
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