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| author | Jay Vosburgh <jay.vosburgh@canonical.com> | 2014-11-14 22:05:06 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-11-15 00:36:25 +0300 |
| commit | a77f9c5dcdf8480a93332792c336fa2bf9d31229 (patch) | |
| tree | 003964de0cc772f361d254385406fa75f3fcbff2 /include/asm-generic | |
| parent | 8cd4313aa775537f724486d5b7503b4d46c9f012 (diff) | |
| download | linux-a77f9c5dcdf8480a93332792c336fa2bf9d31229.tar.xz | |
Revert "fast_hash: avoid indirect function calls"
This reverts commit e5a2c899957659cd1a9f789bc462f9c0b35f5150.
Commit e5a2c899 introduced an alternative_call, arch_fast_hash2,
that selects between __jhash2 and __intel_crc4_2_hash based on the
X86_FEATURE_XMM4_2.
Unfortunately, the alternative_call system does not appear to be
suitable for use with C functions, as register usage is not handled
properly for the called functions. The __jhash2 function in particular
clobbers registers that are not preserved when called via
alternative_call, resulting in a panic for direct callers of
arch_fast_hash2 on older CPUs lacking sse4_2. It is possible that
__intel_crc4_2_hash works merely by chance because it uses fewer
registers.
This commit was suggested as the source of the problem by Jesse
Gross <jesse@nicira.com>.
Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/asm-generic')
| -rw-r--r-- | include/asm-generic/hash.h | 36 |
1 files changed, 2 insertions, 34 deletions
diff --git a/include/asm-generic/hash.h b/include/asm-generic/hash.h index 3c82760ff2a4..b6312843dbd9 100644 --- a/include/asm-generic/hash.h +++ b/include/asm-generic/hash.h @@ -1,41 +1,9 @@ #ifndef __ASM_GENERIC_HASH_H #define __ASM_GENERIC_HASH_H -#include <linux/jhash.h> - -/** - * arch_fast_hash - Caclulates a hash over a given buffer that can have - * arbitrary size. This function will eventually use an - * architecture-optimized hashing implementation if - * available, and trades off distribution for speed. - * - * @data: buffer to hash - * @len: length of buffer in bytes - * @seed: start seed - * - * Returns 32bit hash. - */ -static inline u32 arch_fast_hash(const void *data, u32 len, u32 seed) -{ - return jhash(data, len, seed); -} - -/** - * arch_fast_hash2 - Caclulates a hash over a given buffer that has a - * size that is of a multiple of 32bit words. This - * function will eventually use an architecture- - * optimized hashing implementation if available, - * and trades off distribution for speed. - * - * @data: buffer to hash (must be 32bit padded) - * @len: number of 32bit words - * @seed: start seed - * - * Returns 32bit hash. - */ -static inline u32 arch_fast_hash2(const u32 *data, u32 len, u32 seed) +struct fast_hash_ops; +static inline void setup_arch_fast_hash(struct fast_hash_ops *ops) { - return jhash2(data, len, seed); } #endif /* __ASM_GENERIC_HASH_H */ |