Mikael Pettersson e589ed23dd [ARM] 5218/1: arm: improved futex support ... Linux/ARM currently doesn't support robust or PI futexes. The problem is that the kernel wants to perform certain ops (cmpxchg, set, add, or, andn, xor) atomically on user-space addresses, and ARM's futex.h doesn't support that. This patch adds that support, but only for uniprocessor machines. For UP it's enough to disable preemption to ensure mutual exclusion with other software agents (futexes don't need to care about other hardware agents, fortunately). This patch is based on one posted by Khem Raj on 2007-08-01 <http://marc.info/?l=linux-arm-kernel&m=118599407413016&w=2>. (That patch is included in the -RT kernel patches.) My changes since that version include: * corrected implementation of FUTEX_OP_ANDN (must complement oparg) * added missing memory clobber to futex_atomic_cmpxchg_inatomic() * removed spinlock because it's unnecessary for UP and insufficient for SMP, instead the code is restricted to UP and relies on the fact that pagefault_disable() also disables preemption * coding style cleanups Tested on ARMv5 XScales with the glibc-2.6 nptl test suite. Tested-by: Bruce Ashfield <bruce.ashfield@windriver.com> Signed-off-by: Mikael Pettersson <mikpe@it.uu.se> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>		2008-09-01 12:06:26 +01:00
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asm	[ARM] 5218/1: arm: improved futex support	2008-09-01 12:06:26 +01:00