linux/arch/mips/kernel
Christoph Lameter 35898716b4 mips: Replace __get_cpu_var uses
__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: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
2014-08-26 13:45:51 -04:00
..
.gitignore
8250-platform.c
asm-offsets.c MIPS: save/restore MSACSR register on context switch 2014-08-02 00:06:43 +02:00
binfmt_elfn32.c MIPS: Compat: Fix cputime_to_timeval() arguments in compat binfmt_elf. 2013-06-06 16:11:26 +02:00
binfmt_elfo32.c MIPS: Remove old core dump functions 2014-08-02 00:06:37 +02:00
bmips_vec.S MIPS: Fix gigaton of warning building with microMIPS. 2014-03-31 18:17:12 +02:00
branch.c Merge branch '3.15-fixes' into mips-for-linux-next 2014-06-04 22:53:02 +02:00
cevt-bcm1480.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00
cevt-ds1287.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
cevt-gic.c MIPS: allow GIC clockevent device config from other CPUs 2014-05-02 16:39:11 +01:00
cevt-gt641xx.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
cevt-r4k.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
cevt-sb1250.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00
cevt-txx9.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
cps-vec.S MIPS: smp-cps: duplicate core0 CCA on secondary cores 2014-05-28 16:20:33 +01:00
cpu-bugs64.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00
cpu-probe.c MIPS: detect presence of MAARs 2014-08-02 00:06:45 +02:00
crash_dump.c mips: remove savemaxmem parameter setup 2013-07-03 16:08:03 -07:00
crash.c mips: delete non-required instances of include <linux/init.h> 2014-01-24 22:39:56 +01:00
csrc-bcm1480.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
csrc-gic.c MIPS: Refactor GIC clocksource code. 2013-05-09 17:55:20 +02:00
csrc-ioasic.c MIPS: DECstation HRT initialization rearrangement 2013-09-13 11:56:13 +02:00
csrc-r4k.c
csrc-sb1250.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
early_printk_8250.c MIPS: Add 8250/16550 serial early printk driver 2013-10-29 21:24:36 +01:00
early_printk.c early_printk: consolidate random copies of identical code 2013-04-29 18:28:13 -07:00
entry.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
ftrace.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
genex.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
gpio_txx9.c
head.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
i8253.c
i8259.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
idle.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
irq_cpu.c MIPS: Panic messages should not end in \n. 2013-10-29 21:24:19 +01:00
irq_txx9.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq-gic.c MIPS: GIC: Generalise check for pending interrupts 2014-08-02 00:06:41 +02:00
irq-gt641xx.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq-msc01.c MIPS: MSC: Prevent out-of-bounds writes to MIPS SC ioremap'd region 2014-06-26 10:48:23 +01:00
irq-rm7000.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-06-09 18:10:34 -07:00
jump_label.c
kgdb.c MIPS: kernel: {ftrace,kgdb}: Set correct address limit for cache flushes 2014-03-26 23:09:18 +01:00
kprobes.c mips: Replace __get_cpu_var uses 2014-08-26 13:45:51 -04:00
linux32.c unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE 2013-05-09 13:46:38 -04:00
machine_kexec.c
Makefile MIPS: OCTEON: Enable use of FPU 2014-05-30 21:01:09 +02:00
mcount.S Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
mips_ksyms.c MIPS: checksum: Split the 'copy_user' symbol 2014-03-26 23:09:17 +01:00
mips_machine.c MIPS: move mips_{set,get}_machine_name() to a more generic place 2013-05-08 01:19:07 +02:00
mips-cm.c MIPS: Add generic CM probe & access code 2014-03-06 21:25:22 +01:00
mips-cpc.c MIPS: smp-cps: rework core/VPE initialisation 2014-05-28 16:20:28 +01:00
mips-mt-fpaff.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
mips-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
module-rela.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
module.c MIPS: Use NUMA_NO_NODE instead of -1 for node ID. 2013-10-29 21:24:14 +01:00
octeon_switch.S MIPS: OCTEON: Enable use of FPU 2014-05-30 21:01:09 +02:00
perf_event_mipsxx.c mips: Replace __get_cpu_var uses 2014-08-26 13:45:51 -04:00
perf_event.c
pm-cps.c MIPS: {pm,smp}-cps: use cpu_vpe_id macro 2014-07-30 20:48:42 +02:00
pm.c MIPS: PM: Implement PM helper macros 2014-05-02 16:39:10 +01:00
proc.c MIPS: cpu: Add new cpu option for Hardware Table Walker. 2014-08-02 00:06:38 +02:00
process.c MIPS: consistently clear MSA flags when starting & copying threads 2014-08-02 00:06:45 +02:00
prom.c mips: convert fdt pointers to opaque pointers 2014-04-30 00:59:13 -05:00
ptrace32.c MIPS: Remove asm/user.h 2014-08-02 00:06:37 +02:00
ptrace.c Merge branch '3.16-fixes' into mips-for-linux-next 2014-08-02 00:07:03 +02:00
r4k_fpu.S Revert "MIPS: Save/restore MSA context around signals" 2014-06-26 10:48:18 +01:00
r4k_switch.S MIPS: init upper 64b of vector registers when MSA is first used 2014-08-02 00:06:44 +02:00
r2300_fpu.S MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
r2300_switch.S MIPS: stack protector: Fix per-task canary switch 2013-10-07 15:31:04 +02:00
r6000_fpu.S
relocate_kernel.S MIPS: kdump: Skip walking indirection page for crashkernels 2013-09-05 20:53:37 +02:00
reset.c
rtlx-cmp.c MIPS: APRP: Fix an issue when device_create() fails. 2014-08-01 17:30:35 +02:00
rtlx-mt.c MIPS: APRP: Fix an issue when device_create() fails. 2014-08-01 17:30:35 +02:00
rtlx.c MIPS: APRP: Code formatting clean-ups. 2014-01-22 20:19:02 +01:00
scall32-o32.S Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
scall64-64.S Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
scall64-n32.S Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
scall64-o32.S Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-08-07 08:47:00 -07:00
segment.c MIPS: Add debugfs file to print the segmentation control registers 2014-01-22 20:19:00 +01:00
setup.c MIPS: Add NUMA support for Loongson-3 2014-07-30 21:46:19 +02:00
signal32.c mips: Use sigsp() 2014-08-06 13:04:30 +02:00
signal_n32.c mips: Use sigsp() 2014-08-06 13:04:30 +02:00
signal-common.h mips: Use get_signal() signal_setup_done() 2014-08-06 13:03:08 +02:00
signal.c mips: Use sigsp() 2014-08-06 13:04:30 +02:00
smp-bmips.c mips: Replace __get_cpu_var uses 2014-08-26 13:45:51 -04:00
smp-cmp.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp-cps.c MIPS: smp-cps: Fix entry code cache flush for systems with coherent I/O 2014-07-30 20:49:36 +02:00
smp-gic.c cpuidle: cpuidle-cps: add MIPS CPS cpuidle driver 2014-05-28 16:20:36 +01:00
smp-mt.c MIPS: smp-mt: Fix link error when PROC_FS=n 2014-08-01 18:32:02 +02:00
smp-up.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp.c MIPS: Support CPU topology files in sysfs 2014-07-30 21:45:39 +02:00
spinlock_test.c
spram.c MIPS: Use current_cpu_type() instead of c->cputype 2014-03-31 18:17:12 +02:00
stacktrace.c
sync-r4k.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
syscall.c MIPS: Fix gigaton of warning building with microMIPS. 2014-03-31 18:17:12 +02:00
time.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
topology.c
traps.c MIPS: disable preemption whilst initialising MSA 2014-08-02 00:06:44 +02:00
unaligned.c MIPS: Remove BUG_ON(!is_fpu_owner()) in do_ade() 2014-07-30 21:30:22 +02:00
vdso.c
vmlinux.lds.S MIPS: Discard .eh_frame sections in linker script. 2013-08-26 15:33:41 +02:00
vpe-cmp.c MIPS: APRP: Add VPE loader support for CMP platforms. 2014-01-22 20:19:02 +01:00
vpe-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
vpe.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-01-30 17:20:32 -08:00
watch.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00