a750036f35
With the write lock path simply subtracting RW_LOCK_BIAS there is, on large systems, the theoretical possibility of overflowing the 32-bit value that was used so far (namely if 128 or more CPUs manage to do the subtraction, but don't get to do the inverse addition in the failure path quickly enough). A first measure is to modify RW_LOCK_BIAS itself - with the new value chosen, it is good for up to 2048 CPUs each allowed to nest over 2048 times on the read path without causing an issue. Quite possibly it would even be sufficient to adjust the bias a little further, assuming that allowing for significantly less nesting would suffice. However, as the original value chosen allowed for even more nesting levels, to support more than 2048 CPUs (possible currently only for 64-bit kernels) the lock itself gets widened to 64 bits. Signed-off-by: Jan Beulich <jbeulich@novell.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/4E258E0D020000780004E3F0@nat28.tlf.novell.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
58 lines
1.4 KiB
C
58 lines
1.4 KiB
C
#ifndef _ASM_X86_ASM_H
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#define _ASM_X86_ASM_H
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#ifdef __ASSEMBLY__
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# define __ASM_FORM(x) x
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# define __ASM_FORM_COMMA(x) x,
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# define __ASM_EX_SEC .section __ex_table, "a"
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#else
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# define __ASM_FORM(x) " " #x " "
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# define __ASM_FORM_COMMA(x) " " #x ","
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# define __ASM_EX_SEC " .section __ex_table,\"a\"\n"
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#endif
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#ifdef CONFIG_X86_32
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# define __ASM_SEL(a,b) __ASM_FORM(a)
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#else
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# define __ASM_SEL(a,b) __ASM_FORM(b)
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#endif
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#define __ASM_SIZE(inst, ...) __ASM_SEL(inst##l##__VA_ARGS__, \
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inst##q##__VA_ARGS__)
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#define __ASM_REG(reg) __ASM_SEL(e##reg, r##reg)
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#define _ASM_PTR __ASM_SEL(.long, .quad)
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#define _ASM_ALIGN __ASM_SEL(.balign 4, .balign 8)
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#define _ASM_MOV __ASM_SIZE(mov)
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#define _ASM_INC __ASM_SIZE(inc)
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#define _ASM_DEC __ASM_SIZE(dec)
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#define _ASM_ADD __ASM_SIZE(add)
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#define _ASM_SUB __ASM_SIZE(sub)
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#define _ASM_XADD __ASM_SIZE(xadd)
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#define _ASM_AX __ASM_REG(ax)
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#define _ASM_BX __ASM_REG(bx)
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#define _ASM_CX __ASM_REG(cx)
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#define _ASM_DX __ASM_REG(dx)
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#define _ASM_SP __ASM_REG(sp)
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#define _ASM_BP __ASM_REG(bp)
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#define _ASM_SI __ASM_REG(si)
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#define _ASM_DI __ASM_REG(di)
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/* Exception table entry */
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#ifdef __ASSEMBLY__
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# define _ASM_EXTABLE(from,to) \
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__ASM_EX_SEC ; \
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_ASM_ALIGN ; \
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_ASM_PTR from , to ; \
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.previous
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#else
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# define _ASM_EXTABLE(from,to) \
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__ASM_EX_SEC \
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_ASM_ALIGN "\n" \
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_ASM_PTR #from "," #to "\n" \
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" .previous\n"
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#endif
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#endif /* _ASM_X86_ASM_H */
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