__get_cpu_var() is used for multiple purposes in the kernel source. One of
them is address calculation via the form &__get_cpu_var(x). This calculates
the address for the instance of the percpu variable of the current processor
based on an offset.
Other use cases are for storing and retrieving data from the current
processors percpu area. __get_cpu_var() can be used as an lvalue when
writing data or on the right side of an assignment.
__get_cpu_var() is defined as :
#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))
__get_cpu_var() always only does an address determination. However, store
and retrieve operations could use a segment prefix (or global register on
other platforms) to avoid the address calculation.
this_cpu_write() and this_cpu_read() can directly take an offset into a
percpu area and use optimized assembly code to read and write per cpu
variables.
This patch converts __get_cpu_var into either an explicit address
calculation using this_cpu_ptr() or into a use of this_cpu operations that
use the offset. Thereby address calculations are avoided and less registers
are used when code is generated.
At the end of the patch set all uses of __get_cpu_var have been removed so
the macro is removed too.
The patch set includes passes over all arches as well. Once these operations
are used throughout then specialized macros can be defined in non -x86
arches as well in order to optimize per cpu access by f.e. using a global
register that may be set to the per cpu base.
Transformations done to __get_cpu_var()
1. Determine the address of the percpu instance of the current processor.
DEFINE_PER_CPU(int, y);
int *x = &__get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(&y);
2. Same as #1 but this time an array structure is involved.
DEFINE_PER_CPU(int, y[20]);
int *x = __get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(y);
3. Retrieve the content of the current processors instance of a per cpu
variable.
DEFINE_PER_CPU(int, y);
int x = __get_cpu_var(y)
Converts to
int x = __this_cpu_read(y);
4. Retrieve the content of a percpu struct
DEFINE_PER_CPU(struct mystruct, y);
struct mystruct x = __get_cpu_var(y);
Converts to
memcpy(&x, this_cpu_ptr(&y), sizeof(x));
5. Assignment to a per cpu variable
DEFINE_PER_CPU(int, y)
__get_cpu_var(y) = x;
Converts to
__this_cpu_write(y, x);
6. Increment/Decrement etc of a per cpu variable
DEFINE_PER_CPU(int, y);
__get_cpu_var(y)++
Converts to
__this_cpu_inc(y)
Cc: sparclinux@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Fix following sparc32 warning:
cpu.c:430:29: warning: symbol 'cpuinfo_op' was not declared. Should it be static?
Fix following sparc64 warnings:
cpu.c:364:14: warning: symbol 'dcache_parity_tl1_occurred' was not declared. Should it be static?
cpu.c:365:14: warning: symbol 'icache_parity_tl1_occurred' was not declared. Should it be static?
Rearrange asm/cpu.h to share more stuff between sparc32 and sparc64.
Added missing include to cpu.c of kernel.h
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This keeps us from having to use kstat_irqs_cpu() from the NMI handler,
the former of which is a profiled function.
Instead we use a currently empty slot in the cpu_data
Signed-off-by: David S. Miller <davem@davemloft.net>
Later we're going to want to get at these definitions from
asm/percpu.h and that's not possible via cpudata.h because
of the set of dependencies the non-trap_block[] stuff has.
Signed-off-by: David S. Miller <davem@davemloft.net>
This really isn't necessary at all, a local variable suits the
job just fine.
This frees up 8 bytes in the trap_block[] that we can use later
to store the per-cpu base addresses.
Signed-off-by: David S. Miller <davem@davemloft.net>
Three main things:
1) Make prober an arch initcall instead of using hard-coded invocation
from paging_init()
2) Shrink table size, the fpu ident stuff was never used.
3) Use named struct initialized in table.
Signed-off-by: David S. Miller <davem@davemloft.net>
The majority of this patch was created by the following script:
***
ASM=arch/sparc/include/asm
mkdir -p $ASM
git mv include/asm-sparc64/ftrace.h $ASM
git rm include/asm-sparc64/*
git mv include/asm-sparc/* $ASM
sed -ie 's/asm-sparc64/asm/g' $ASM/*
sed -ie 's/asm-sparc/asm/g' $ASM/*
***
The rest was an update of the top-level Makefile to use sparc
for header files when sparc64 is being build.
And a small fixlet to pick up the correct unistd.h from
sparc64 code.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Christoph Lameter