On some CPUs, it is more efficient to disable and enable interrupts in the
kernel rather than use ll/sc for atomic operations. But if we were to set
cpu_has_llsc to false, we would break the userspace futex interface (in
asm/futex.h).
We separate the two concepts, with a new predicate kernel_uses_llsc, that
lets us disable the kernel's use of ll/sc while still allowing the futex
code to use it.
Also there were a couple of cases in bitops.h where we were using ll/sc
unconditionally even if cpu_has_llsc were false.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
The existing asm-generic/atomic.h only defines the
atomic_long type. This renames it to atomic-long.h
so we have a place to add a truly generic atomic.h
that can be used on all non-SMP systems.
Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
This shaves of 1912 bytes of an IP27 defconfig kernel and avoids
unexpected overflow behaviour in atomic_sub_if_positive. Apply the same
changes to the atomic64_* functions for consistency.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
The atomic_t type cannot currently be used in some header files because it
would create an include loop with asm/atomic.h. Move the type definition
to linux/types.h to break the loop.
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
