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94ee12b507
__cmpxchg_small erroneously uses u8 for load comparison which can
be either char or short. This patch changes the local variable to
u32 which is sufficiently sized, as the loaded value is already
masked and shifted appropriately. Using an integer size avoids
any unnecessary canonicalization from use of non native widths.
This patch is part of a series that adapts the MIPS small word
atomics code for xchg and cmpxchg on short and char to RISC-V.
Cc: RISC-V Patches <patches@groups.riscv.org>
Cc: Linux RISC-V <linux-riscv@lists.infradead.org>
Cc: Linux MIPS <linux-mips@linux-mips.org>
Signed-off-by: Michael Clark <michaeljclark@mac.com>
[paul.burton@mips.com:
- Fix varialble typo per Jonas Gorski.
- Consolidate load variable with other declarations.]
Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 3ba7f44d2b ("MIPS: cmpxchg: Implement 1 byte & 2 byte cmpxchg()")
Cc: stable@vger.kernel.org # v4.13+
108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
/*
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* Copyright (C) 2017 Imagination Technologies
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* Author: Paul Burton <paul.burton@mips.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*/
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#include <linux/bitops.h>
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#include <asm/cmpxchg.h>
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unsigned long __xchg_small(volatile void *ptr, unsigned long val, unsigned int size)
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{
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u32 old32, new32, load32, mask;
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volatile u32 *ptr32;
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unsigned int shift;
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/* Check that ptr is naturally aligned */
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WARN_ON((unsigned long)ptr & (size - 1));
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/* Mask value to the correct size. */
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mask = GENMASK((size * BITS_PER_BYTE) - 1, 0);
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val &= mask;
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/*
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* Calculate a shift & mask that correspond to the value we wish to
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* exchange within the naturally aligned 4 byte integerthat includes
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* it.
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*/
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shift = (unsigned long)ptr & 0x3;
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if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
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shift ^= sizeof(u32) - size;
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shift *= BITS_PER_BYTE;
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mask <<= shift;
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/*
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* Calculate a pointer to the naturally aligned 4 byte integer that
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* includes our byte of interest, and load its value.
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*/
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ptr32 = (volatile u32 *)((unsigned long)ptr & ~0x3);
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load32 = *ptr32;
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do {
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old32 = load32;
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new32 = (load32 & ~mask) | (val << shift);
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load32 = cmpxchg(ptr32, old32, new32);
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} while (load32 != old32);
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return (load32 & mask) >> shift;
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}
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unsigned long __cmpxchg_small(volatile void *ptr, unsigned long old,
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unsigned long new, unsigned int size)
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{
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u32 mask, old32, new32, load32, load;
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volatile u32 *ptr32;
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unsigned int shift;
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/* Check that ptr is naturally aligned */
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WARN_ON((unsigned long)ptr & (size - 1));
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/* Mask inputs to the correct size. */
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mask = GENMASK((size * BITS_PER_BYTE) - 1, 0);
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old &= mask;
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new &= mask;
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/*
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* Calculate a shift & mask that correspond to the value we wish to
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* compare & exchange within the naturally aligned 4 byte integer
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* that includes it.
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*/
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shift = (unsigned long)ptr & 0x3;
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if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
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shift ^= sizeof(u32) - size;
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shift *= BITS_PER_BYTE;
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mask <<= shift;
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/*
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* Calculate a pointer to the naturally aligned 4 byte integer that
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* includes our byte of interest, and load its value.
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*/
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ptr32 = (volatile u32 *)((unsigned long)ptr & ~0x3);
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load32 = *ptr32;
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while (true) {
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/*
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* Ensure the byte we want to exchange matches the expected
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* old value, and if not then bail.
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*/
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load = (load32 & mask) >> shift;
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if (load != old)
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return load;
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/*
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* Calculate the old & new values of the naturally aligned
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* 4 byte integer that include the byte we want to exchange.
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* Attempt to exchange the old value for the new value, and
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* return if we succeed.
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*/
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old32 = (load32 & ~mask) | (old << shift);
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new32 = (load32 & ~mask) | (new << shift);
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load32 = cmpxchg(ptr32, old32, new32);
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if (load32 == old32)
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return old;
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}
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}
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