From b3ca1c10d7b32fdfdfaf5484eda486323f52d9be Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Mon, 7 Apr 2014 15:39:34 -0700 Subject: percpu: add raw_cpu_ops The kernel has never been audited to ensure that this_cpu operations are consistently used throughout the kernel. The code generated in many places can be improved through the use of this_cpu operations (which uses a segment register for relocation of per cpu offsets instead of performing address calculations). The patch set also addresses various consistency issues in general with the per cpu macros. A. The semantics of __this_cpu_ptr() differs from this_cpu_ptr only because checks are skipped. This is typically shown through a raw_ prefix. So this patch set changes the places where __this_cpu_ptr() is used to raw_cpu_ptr(). B. There has been the long term wish by some that __this_cpu operations would check for preemption. However, there are cases where preemption checks need to be skipped. This patch set adds raw_cpu operations that do not check for preemption and then adds preemption checks to the __this_cpu operations. C. The use of __get_cpu_var is always a reference to a percpu variable that can also be handled via a this_cpu operation. This patch set replaces all uses of __get_cpu_var with this_cpu operations. D. We can then use this_cpu RMW operations in various places replacing sequences of instructions by a single one. E. The use of this_cpu operations throughout will allow other arches than x86 to implement optimized references and RMV operations to work with per cpu local data. F. The use of this_cpu operations opens up the possibility to further optimize code that relies on synchronization through per cpu data. The patch set works in a couple of stages: I. Patch 1 adds the additional raw_cpu operations and raw_cpu_ptr(). Also converts the existing __this_cpu_xx_# primitive in the x86 code to raw_cpu_xx_#. II. Patch 2-4 use the raw_cpu operations in places that would give us false positives once they are enabled. III. Patch 5 adds preemption checks to __this_cpu operations to allow checking if preemption is properly disabled when these functions are used. IV. Patches 6-20 are patches that simply replace uses of __get_cpu_var with this_cpu_ptr. They do not depend on any changes to the percpu code. No preemption tests are skipped if they are applied. V. Patches 21-46 are conversion patches that use this_cpu operations in various kernel subsystems/drivers or arch code. VI. Patches 47/48 (not included in this series) remove no longer used functions (__this_cpu_ptr and __get_cpu_var). These should only be applied after all the conversion patches have made it and after we have done additional passes through the kernel to ensure that none of the uses of these functions remain. This patch (of 46): The patches following this one will add preemption checks to __this_cpu ops so we need to have an alternative way to use this_cpu operations without preemption checks. raw_cpu_ops will be the basis for all other ops since these will be the operations that do not implement any checks. Primitive operations are renamed by this patch from __this_cpu_xxx to raw_cpu_xxxx. Also change the uses of the x86 percpu primitives in preempt.h. These depend directly on asm/percpu.h (header #include nesting issue). Signed-off-by: Peter Zijlstra Signed-off-by: Christoph Lameter Acked-by: Ingo Molnar Cc: Tejun Heo Cc: "James E.J. Bottomley" Cc: "Paul E. McKenney" Cc: Alex Shi Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Bryan Wu Cc: Catalin Marinas Cc: Chris Metcalf Cc: Daniel Lezcano Cc: David Daney Cc: David Miller Cc: David S. Miller Cc: Dimitri Sivanich Cc: Dipankar Sarma Cc: Eric Dumazet Cc: Fenghua Yu Cc: Frederic Weisbecker Cc: Greg Kroah-Hartman Cc: H. Peter Anvin Cc: Haavard Skinnemoen Cc: Hans-Christian Egtvedt Cc: Hedi Berriche Cc: Heiko Carstens Cc: Helge Deller Cc: Ivan Kokshaysky Cc: James Hogan Cc: Jens Axboe Cc: John Stultz Cc: Martin Schwidefsky Cc: Masami Hiramatsu Cc: Matt Turner Cc: Mike Frysinger Cc: Mike Travis Cc: Neil Brown Cc: Nicolas Pitre Cc: Paul Mackerras Cc: Paul Mundt Cc: Rafael J. Wysocki Cc: Ralf Baechle Cc: Richard Henderson Cc: Robert Richter Cc: Russell King Cc: Russell King Cc: Rusty Russell Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Tony Luck Cc: Will Deacon Cc: Wim Van Sebroeck Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/percpu.h | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h index d17784ea37ff..0703aa75b5e8 100644 --- a/include/asm-generic/percpu.h +++ b/include/asm-generic/percpu.h @@ -56,17 +56,17 @@ extern unsigned long __per_cpu_offset[NR_CPUS]; #define per_cpu(var, cpu) \ (*SHIFT_PERCPU_PTR(&(var), per_cpu_offset(cpu))) -#ifndef __this_cpu_ptr -#define __this_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, __my_cpu_offset) +#ifndef raw_cpu_ptr +#define raw_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, __my_cpu_offset) #endif #ifdef CONFIG_DEBUG_PREEMPT #define this_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, my_cpu_offset) #else -#define this_cpu_ptr(ptr) __this_cpu_ptr(ptr) +#define this_cpu_ptr(ptr) raw_cpu_ptr(ptr) #endif #define __get_cpu_var(var) (*this_cpu_ptr(&(var))) -#define __raw_get_cpu_var(var) (*__this_cpu_ptr(&(var))) +#define __raw_get_cpu_var(var) (*raw_cpu_ptr(&(var))) #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA extern void setup_per_cpu_areas(void); @@ -83,7 +83,7 @@ extern void setup_per_cpu_areas(void); #define __get_cpu_var(var) (*VERIFY_PERCPU_PTR(&(var))) #define __raw_get_cpu_var(var) (*VERIFY_PERCPU_PTR(&(var))) #define this_cpu_ptr(ptr) per_cpu_ptr(ptr, 0) -#define __this_cpu_ptr(ptr) this_cpu_ptr(ptr) +#define raw_cpu_ptr(ptr) this_cpu_ptr(ptr) #endif /* SMP */ @@ -122,4 +122,7 @@ extern void setup_per_cpu_areas(void); #define PER_CPU_DEF_ATTRIBUTES #endif +/* Keep until we have removed all uses of __this_cpu_ptr */ +#define __this_cpu_ptr raw_cpu_ptr + #endif /* _ASM_GENERIC_PERCPU_H_ */ -- cgit v1.2.1