![]() - 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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.. | ||
bitops | ||
4level-fixup.h | ||
atomic.h | ||
audit_change_attr.h | ||
audit_dir_write.h | ||
audit_read.h | ||
audit_signal.h | ||
audit_write.h | ||
bitops.h | ||
bug.h | ||
cmpxchg-local.h | ||
cmpxchg.h | ||
cputime.h | ||
device.h | ||
div64.h | ||
dma-coherent.h | ||
dma-mapping-broken.h | ||
dma-mapping.h | ||
emergency-restart.h | ||
errno-base.h | ||
errno.h | ||
fcntl.h | ||
futex.h | ||
gpio.h | ||
ide_iops.h | ||
int-l64.h | ||
int-ll64.h | ||
ioctl.h | ||
iomap.h | ||
irq_regs.h | ||
Kbuild | ||
Kbuild.asm | ||
kdebug.h | ||
libata-portmap.h | ||
local.h | ||
memory_model.h | ||
mm_hooks.h | ||
mman.h | ||
mutex-dec.h | ||
mutex-null.h | ||
mutex-xchg.h | ||
page.h | ||
pci-dma-compat.h | ||
pci.h | ||
percpu.h | ||
pgtable-nopmd.h | ||
pgtable-nopud.h | ||
pgtable.h | ||
poll.h | ||
resource.h | ||
rtc.h | ||
sections.h | ||
siginfo.h | ||
signal.h | ||
statfs.h | ||
syscall.h | ||
termios.h | ||
tlb.h | ||
topology.h | ||
uaccess.h | ||
vmlinux.lds.h | ||
xor.h |