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* x86, percpu: Add 'percpu_read_stable()' interface for cacheable accessesLinus Torvalds2009-08-041-1/+1
| | | | | | | | | | | | | | | | This is very useful for some common things like 'get_current()' and 'get_thread_info()', which can be used multiple times in a function, and where the result is cacheable. tj: Added the magical undocumented "P" modifier to UP __percpu_arg() to force gcc to dereference the pointer value passed in via the "p" input constraint. Without this, percpu_read_stable() returns the address of the percpu variable. Also added comment explaining the difference between percpu_read() and percpu_read_stable(). Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
* x86-64: Move current task from PDA to per-cpu and consolidate with 32-bit.Brian Gerst2009-01-191-21/+3
| | | | | Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* percpu: add optimized generic percpu accessorsIngo Molnar2009-01-161-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It is an optimization and a cleanup, and adds the following new generic percpu methods: percpu_read() percpu_write() percpu_add() percpu_sub() percpu_and() percpu_or() percpu_xor() and implements support for them on x86. (other architectures will fall back to a default implementation) The advantage is that for example to read a local percpu variable, instead of this sequence: return __get_cpu_var(var); ffffffff8102ca2b: 48 8b 14 fd 80 09 74 mov -0x7e8bf680(,%rdi,8),%rdx ffffffff8102ca32: 81 ffffffff8102ca33: 48 c7 c0 d8 59 00 00 mov $0x59d8,%rax ffffffff8102ca3a: 48 8b 04 10 mov (%rax,%rdx,1),%rax We can get a single instruction by using the optimized variants: return percpu_read(var); ffffffff8102ca3f: 65 48 8b 05 91 8f fd mov %gs:0x7efd8f91(%rip),%rax I also cleaned up the x86-specific APIs and made the x86 code use these new generic percpu primitives. tj: * fixed generic percpu_sub() definition as Roel Kluin pointed out * added percpu_and() for completeness's sake * made generic percpu ops atomic against preemption Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Tejun Heo <tj@kernel.org>
* x86: Fix ASM_X86__ header guardsH. Peter Anvin2008-10-221-3/+3
| | | | | | | | | Change header guards named "ASM_X86__*" to "_ASM_X86_*" since: a. the double underscore is ugly and pointless. b. no leading underscore violates namespace constraints. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
* x86, um: ... and asm-x86 moveAl Viro2008-10-221-0/+39
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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