linux/include/asm-generic/percpu.h, branch v3.7-rc7

percpu: Optimize __get_cpu_var()

2010-09-10T08:56:51Z

Redefine __get_cpu_var() using this_cpu_ptr() which can be arch-optimized. Signed-off-by: Brian Gerst Signed-off-by: Tejun Heo

x86, percpu: Optimize this_cpu_ptr

2010-09-10T08:56:47Z

Allow arches to implement __this_cpu_ptr, and provide an x86 version. Before: movq $foo, %rax movq %gs:this_cpu_off, %rdx addq %rdx, %rax After: movq $foo, %rax addq %gs:this_cpu_off, %rax The benefit is doing it in one less instruction and not clobbering a temporary register. tj: * Beefed up the comment a bit and renamed in-macro temp variable to match neighboring macros. * Folded fix for const pointer case found in linux-next. * Fixed sparse notation. Signed-off-by: Brian Gerst Signed-off-by: Tejun Heo

percpu: handle __percpu notations in UP accessors

2010-08-07T12:20:53Z

UP accessors didn't take care of __percpu notations leading to a lot of spurious sparse warnings on UP configurations. Fix it. Signed-off-by: Namhyung Kim Signed-off-by: Tejun Heo

Merge branch 'for-35' of git://repo.or.cz/linux-kbuild

2010-06-01T15:55:52Z

* 'for-35' of git://repo.or.cz/linux-kbuild: (81 commits) kbuild: Revert part of e8d400a to resolve a conflict kbuild: Fix checking of scm-identifier variable gconfig: add support to show hidden options that have prompts menuconfig: add support to show hidden options which have prompts gconfig: remove show_debug option gconfig: remove dbg_print_ptype() and dbg_print_stype() kconfig: fix zconfdump() kconfig: some small fixes add random binaries to .gitignore kbuild: Include gen_initramfs_list.sh and the file list in the .d file kconfig: recalc symbol value before showing search results .gitignore: ignore *.lzo files headerdep: perlcritic warning scripts/Makefile.lib: Align the output of LZO kbuild: Generate modules.builtin in make modules_install Revert "kbuild: specify absolute paths for cscope" kbuild: Do not unnecessarily regenerate modules.builtin headers_install: use local file handles headers_check: fix perl warnings export_report: fix perl warnings ...

Rename .data[.percpu][.XXX] to .data[..percpu][..XXX].

2010-03-03T10:26:00Z

Signed-off-by: Denys Vlasenko Signed-off-by: Michal Marek

percpu: make accessors check for percpu pointer in sparse

2009-10-29T13:34:15Z

The previous patch made sparse warn about percpu variables being used directly without going through percpu accessors. This patch implements the other half - checking whether non percpu variable is passed into percpu accessors. Signed-off-by: Tejun Heo Cc: Rusty Russell Cc: Al Viro

percpu: add __percpu for sparse.

2009-10-29T13:34:15Z

We have to make __kernel "__attribute__((address_space(0)))" so we can cast to it. tj: * put_cpu_var() update. * Annotations added to dynamic allocator interface. Signed-off-by: Rusty Russell Cc: Al Viro Signed-off-by: Tejun Heo

percpu: remove per_cpu__ prefix.

2009-10-29T13:34:15Z

Now that the return from alloc_percpu is compatible with the address of per-cpu vars, it makes sense to hand around the address of per-cpu variables. To make this sane, we remove the per_cpu__ prefix we used created to stop people accidentally using these vars directly. Now we have sparse, we can use that (next patch). tj: * Updated to convert stuff which were missed by or added after the original patch. * Kill per_cpu_var() macro. Signed-off-by: Rusty Russell Signed-off-by: Tejun Heo Reviewed-by: Christoph Lameter

this_cpu: Introduce this_cpu_ptr() and generic this_cpu_* operations

2009-10-03T10:48:22Z

This patch introduces two things: First this_cpu_ptr and then per cpu atomic operations. this_cpu_ptr ------------ A common operation when dealing with cpu data is to get the instance of the cpu data associated with the currently executing processor. This can be optimized by this_cpu_ptr(xx) = per_cpu_ptr(xx, smp_processor_id). The problem with per_cpu_ptr(x, smp_processor_id) is that it requires an array lookup to find the offset for the cpu. Processors typically have the offset for the current cpu area in some kind of (arch dependent) efficiently accessible register or memory location. We can use that instead of doing the array lookup to speed up the determination of the address of the percpu variable. This is particularly significant because these lookups occur in performance critical paths of the core kernel. this_cpu_ptr() can avoid memory accesses and this_cpu_ptr comes in two flavors. The preemption context matters since we are referring the the currently executing processor. In many cases we must insure that the processor does not change while a code segment is executed. __this_cpu_ptr -> Do not check for preemption context this_cpu_ptr -> Check preemption context The parameter to these operations is a per cpu pointer. This can be the address of a statically defined per cpu variable (&per_cpu_var(xxx)) or the address of a per cpu variable allocated with the per cpu allocator. per cpu atomic operations: this_cpu_*(var, val) ----------------------------------------------- this_cpu_* operations (like this_cpu_add(struct->y, value) operate on abitrary scalars that are members of structures allocated with the new per cpu allocator. They can also operate on static per_cpu variables if they are passed to per_cpu_var() (See patch to use this_cpu_* operations for vm statistics). These operations are guaranteed to be atomic vs preemption when modifying the scalar. The calculation of the per cpu offset is also guaranteed to be atomic at the same time. This means that a this_cpu_* operation can be safely used to modify a per cpu variable in a context where interrupts are enabled and preemption is allowed. Many architectures can perform such a per cpu atomic operation with a single instruction. Note that the atomicity here is different from regular atomic operations. Atomicity is only guaranteed for data accessed from the currently executing processor. Modifications from other processors are still possible. There must be other guarantees that the per cpu data is not modified from another processor when using these instruction. The per cpu atomicity is created by the fact that the processor either executes and instruction or not. Embedded in the instruction is the relocation of the per cpu address to the are reserved for the current processor and the RMW action. Therefore interrupts or preemption cannot occur in the mids of this processing. Generic fallback functions are used if an arch does not define optimized this_cpu operations. The functions come also come in the two flavors used for this_cpu_ptr(). The firstparameter is a scalar that is a member of a structure allocated through allocpercpu or a per cpu variable (use per_cpu_var(xxx)). The operations are similar to what percpu_add() and friends do. this_cpu_read(scalar) this_cpu_write(scalar, value) this_cpu_add(scale, value) this_cpu_sub(scalar, value) this_cpu_inc(scalar) this_cpu_dec(scalar) this_cpu_and(scalar, value) this_cpu_or(scalar, value) this_cpu_xor(scalar, value) Arch code can override the generic functions and provide optimized atomic per cpu operations. These atomic operations must provide both the relocation (x86 does it through a segment override) and the operation on the data in a single instruction. Otherwise preempt needs to be disabled and there is no gain from providing arch implementations. A third variant is provided prefixed by irqsafe_. These variants are safe against hardware interrupts on the *same* processor (all per cpu atomic primitives are *always* *only* providing safety for code running on the *same* processor!). The increment needs to be implemented by the hardware in such a way that it is a single RMW instruction that is either processed before or after an interrupt. cc: David Howells cc: Ingo Molnar cc: Rusty Russell cc: Eric Dumazet Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo

x86/i386: Put aligned stack-canary in percpu shared_aligned section

2009-09-04T05:10:31Z

Pack aligned things together into a special section to minimize padding holes. Suggested-by: Eric Dumazet Signed-off-by: Jeremy Fitzhardinge Cc: Tejun Heo LKML-Reference: <4AA035C0.9070202@goop.org> [ queued up in tip:x86/asm because it depends on this commit: x86/i386: Make sure stack-protector segment base is cache aligned ] Signed-off-by: Ingo Molnar