a8ddac7e53
- atomic operations which both modify the variable and return something imply full smp memory barriers before and after the memory operations involved (failing atomic_cmpxchg, atomic_add_unless, etc don't imply a barrier because they don't modify the target). See Documentation/atomic_ops.txt. So remove extra barriers and branches. - All architectures support atomic_cmpxchg. This has no relation to __HAVE_ARCH_CMPXCHG. We can just take the atomic_cmpxchg path unconditionally This reduces a simple single threaded fastpath lock+unlock test from 590 cycles to 203 cycles on a ppc970 system. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| acpi | ||
| asm-arm | ||
| asm-cris | ||
| asm-frv | ||
| asm-generic | ||
| asm-h8300 | ||
| asm-m32r | ||
| asm-m68k | ||
| asm-mn10300 | ||
| asm-um | ||
| asm-x86 | ||
| asm-xtensa | ||
| crypto | ||
| drm | ||
| keys | ||
| linux | ||
| math-emu | ||
| media | ||
| mtd | ||
| net | ||
| pcmcia | ||
| rdma | ||
| rxrpc | ||
| scsi | ||
| sound | ||
| trace | ||
| video | ||
| xen | ||
| Kbuild | ||