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>
75 lines
2 KiB
C
75 lines
2 KiB
C
/* include/asm-i386/rwlock.h
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*
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* Helpers used by both rw spinlocks and rw semaphores.
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*
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* Based in part on code from semaphore.h and
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* spinlock.h Copyright 1996 Linus Torvalds.
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*
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* Copyright 1999 Red Hat, Inc.
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*
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* Written by Benjamin LaHaise.
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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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#ifndef _ASM_I386_RWLOCK_H
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#define _ASM_I386_RWLOCK_H
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#define RW_LOCK_BIAS 0x01000000
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#define RW_LOCK_BIAS_STR "0x01000000"
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#define __build_read_lock_ptr(rw, helper) \
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alternative_smp("lock; subl $1,(%0)\n\t" \
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"jns 1f\n" \
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"call " helper "\n\t" \
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"1:\n", \
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"subl $1,(%0)\n\t", \
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:"a" (rw) : "memory")
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#define __build_read_lock_const(rw, helper) \
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alternative_smp("lock; subl $1,%0\n\t" \
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"jns 1f\n" \
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"pushl %%eax\n\t" \
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"leal %0,%%eax\n\t" \
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"call " helper "\n\t" \
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"popl %%eax\n\t" \
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"1:\n", \
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"subl $1,%0\n\t", \
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"=m" (*(volatile int *)rw) : : "memory")
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#define __build_read_lock(rw, helper) do { \
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if (__builtin_constant_p(rw)) \
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__build_read_lock_const(rw, helper); \
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else \
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__build_read_lock_ptr(rw, helper); \
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} while (0)
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#define __build_write_lock_ptr(rw, helper) \
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alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
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"jz 1f\n" \
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"call " helper "\n\t" \
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"1:\n", \
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"subl $" RW_LOCK_BIAS_STR ",(%0)\n\t", \
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:"a" (rw) : "memory")
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#define __build_write_lock_const(rw, helper) \
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alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
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"jz 1f\n" \
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"pushl %%eax\n\t" \
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"leal %0,%%eax\n\t" \
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"call " helper "\n\t" \
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"popl %%eax\n\t" \
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"1:\n", \
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"subl $" RW_LOCK_BIAS_STR ",%0\n\t", \
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"=m" (*(volatile int *)rw) : : "memory")
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#define __build_write_lock(rw, helper) do { \
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if (__builtin_constant_p(rw)) \
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__build_write_lock_const(rw, helper); \
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else \
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__build_write_lock_ptr(rw, helper); \
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} while (0)
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#endif
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