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authorChristoph Lameter <cl@linux.com>2014-10-21 15:23:25 -0500
committerMichael Ellerman <mpe@ellerman.id.au>2014-11-03 12:12:32 +1100
commit69111bac42f5ceacdd22e30947837ceb2c4493ed (patch)
tree717c5e3c231b078f970aeb5d895bd96f9efc8fdd /arch/powerpc/kernel/smp.c
parent0df1f2487d2f0d04703f142813d53615d62a1da4 (diff)
powerpc: Replace __get_cpu_var uses
This still has not been merged and now powerpc is the only arch that does not have this change. Sorry about missing linuxppc-dev before. V2->V2 - Fix up to work against 3.18-rc1 __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 : __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: Benjamin Herrenschmidt <benh@kernel.crashing.org> CC: Paul Mackerras <paulus@samba.org> Signed-off-by: Christoph Lameter <cl@linux.com> [mpe: Fix build errors caused by set/or_softirq_pending(), and rework assignment in __set_breakpoint() to use memcpy().] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/smp.c')
-rw-r--r--arch/powerpc/kernel/smp.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 71e186d5f331..8b2d2dc8ef10 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -243,7 +243,7 @@ void smp_muxed_ipi_message_pass(int cpu, int msg)
irqreturn_t smp_ipi_demux(void)
{
- struct cpu_messages *info = &__get_cpu_var(ipi_message);
+ struct cpu_messages *info = this_cpu_ptr(&ipi_message);
unsigned int all;
mb(); /* order any irq clear */
@@ -442,9 +442,9 @@ void generic_mach_cpu_die(void)
idle_task_exit();
cpu = smp_processor_id();
printk(KERN_DEBUG "CPU%d offline\n", cpu);
- __get_cpu_var(cpu_state) = CPU_DEAD;
+ __this_cpu_write(cpu_state, CPU_DEAD);
smp_wmb();
- while (__get_cpu_var(cpu_state) != CPU_UP_PREPARE)
+ while (__this_cpu_read(cpu_state) != CPU_UP_PREPARE)
cpu_relax();
}