Support an option
CONFIG_PERCPU_ZERO_BASED
that makes offsets for per cpu variables start at zero.
If a percpu area starts at zero then
1. We do not need RELOC_HIDE anymore
2. Indexes off the per cpu area for each processor are small
3. The percpu area "addresses" are offsets and we can then
have allocpercpu/cpu_alloc in the future also use these
offsets so that percpu functions can take any type of
percpu address if it is provided by a percpu variable
or a pointer obtained via allocpercpu/cpu_alloc.
The linker area boundaries variables are different for zero based
percpu segments:
__per_cpu_load -> The address at which the percpu area was loaded
__per_cpu_size -> The length of the per cpu area
Removes the &__per_cpu_x in lockdep. AFAICT The __per_cpu_x are already
pointers.
Signed-off-by: Christoph Lameter <[email protected]>
---
include/asm-generic/percpu.h | 7 ++++++-
include/asm-generic/sections.h | 10 ++++++++++
include/asm-generic/vmlinux.lds.h | 15 +++++++++++++++
init/main.c | 17 +++++++++--------
kernel/lockdep.c | 4 ++--
5 files changed, 42 insertions(+), 11 deletions(-)
Index: linux-2.6.24-rc3-mm2/include/asm-generic/percpu.h
===================================================================
--- linux-2.6.24-rc3-mm2.orig/include/asm-generic/percpu.h 2007-11-29 22:05:58.359576450 -0800
+++ linux-2.6.24-rc3-mm2/include/asm-generic/percpu.h 2007-11-29 22:06:22.750825804 -0800
@@ -42,8 +42,13 @@ extern unsigned long __per_cpu_offset[NR
* Only S390 provides its own means of moving the pointer.
*/
#ifndef SHIFT_PTR
+#ifdef CONFIG_PERCPU_ZERO_BASED
+#define SHIFT_PTR(__p, __offset) \
+ ((__typeof(__p))(((void *)(__p)) + (__offset)))
+#else
#define SHIFT_PTR(__p, __offset) RELOC_HIDE((__p), (__offset))
-#endif
+#endif /* CONFIG_PER_CPU_ZERO_BASED */
+#endif /* SHIFT_PTR */
/*
* A percpu variable may point to a discarded reghions. The following are
Index: linux-2.6.24-rc3-mm2/include/asm-generic/sections.h
===================================================================
--- linux-2.6.24-rc3-mm2.orig/include/asm-generic/sections.h 2007-11-29 22:05:58.367576240 -0800
+++ linux-2.6.24-rc3-mm2/include/asm-generic/sections.h 2007-11-29 22:06:22.754826440 -0800
@@ -9,7 +9,17 @@ extern char __bss_start[], __bss_stop[];
extern char __init_begin[], __init_end[];
extern char _sinittext[], _einittext[];
extern char _end[];
+#ifdef CONFIG_PERCPU_ZERO_BASED
+extern char __per_cpu_load[];
+extern char ____per_cpu_size[];
+#define __per_cpu_size ((unsigned long)&____per_cpu_size)
+#define __per_cpu_start ((char *)0)
+#define __per_cpu_end ((char *)__per_cpu_size)
+#else
extern char __per_cpu_start[], __per_cpu_end[];
+#define __per_cpu_load __per_cpu_start
+#define __per_cpu_size (__per_cpu_end - __per_cpu_start)
+#endif
extern char __kprobes_text_start[], __kprobes_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __start_rodata[], __end_rodata[];
Index: linux-2.6.24-rc3-mm2/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6.24-rc3-mm2.orig/include/asm-generic/vmlinux.lds.h 2007-11-29 22:06:03.486826118 -0800
+++ linux-2.6.24-rc3-mm2/include/asm-generic/vmlinux.lds.h 2007-11-29 22:06:22.754826440 -0800
@@ -255,6 +255,20 @@
*(.initcall7.init) \
*(.initcall7s.init)
+#ifdef CONFIG_PERCPU_ZERO_BASED
+#define PERCPU(align) \
+ . = ALIGN(align); \
+ percpu : { } :percpu \
+ __per_cpu_load = .; \
+ .data.percpu 0 : AT(__per_cpu_load - LOAD_OFFSET) { \
+ *(.data.percpu.first) \
+ *(.data.percpu) \
+ *(.data.percpu.shared_aligned) \
+ ____per_cpu_size = .; \
+ } \
+ . = __per_cpu_load + ____per_cpu_size; \
+ data : { } :data
+#else
#define PERCPU(align) \
. = ALIGN(align); \
__per_cpu_start = .; \
@@ -263,3 +277,4 @@
*(.data.percpu.shared_aligned) \
} \
__per_cpu_end = .;
+#endif
Index: linux-2.6.24-rc3-mm2/init/main.c
===================================================================
--- linux-2.6.24-rc3-mm2.orig/init/main.c 2007-11-29 22:06:01.607326159 -0800
+++ linux-2.6.24-rc3-mm2/init/main.c 2007-11-29 22:06:22.754826440 -0800
@@ -370,18 +370,19 @@ EXPORT_SYMBOL(__per_cpu_offset);
static void __init setup_per_cpu_areas(void)
{
- unsigned long size, i;
- char *ptr;
- unsigned long nr_possible_cpus = num_possible_cpus();
+ unsigned long size;
+ int cpu;
/* Copy section for each CPU (we discard the original) */
size = ALIGN(PERCPU_ENOUGH_ROOM, PAGE_SIZE);
- ptr = alloc_bootmem_pages(size * nr_possible_cpus);
- for_each_possible_cpu(i) {
- __per_cpu_offset[i] = ptr - __per_cpu_start;
- memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
- ptr += size;
+ for_each_possible_cpu(cpu) {
+ char *ptr;
+
+ ptr = alloc_bootmem_pages_node(NODE_DATA(cpu_to_node(cpu)),
+ size);
+ __per_cpu_offset[cpu] = ptr - __per_cpu_start;
+ memcpy(ptr, __per_cpu_load, __per_cpu_size);
}
}
#endif /* CONFIG_ARCH_SETS_UP_CPU_AREA */
Index: linux-2.6.24-rc3-mm2/kernel/lockdep.c
===================================================================
--- linux-2.6.24-rc3-mm2.orig/kernel/lockdep.c 2007-11-29 22:05:58.391576218 -0800
+++ linux-2.6.24-rc3-mm2/kernel/lockdep.c 2007-11-29 22:06:22.754826440 -0800
@@ -613,8 +613,8 @@ static int static_obj(void *obj)
* percpu var?
*/
for_each_possible_cpu(i) {
- start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
- end = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
+ start = (unsigned long) __per_cpu_start + per_cpu_offset(i);
+ end = (unsigned long) __per_cpu_start + PERCPU_ENOUGH_ROOM
+ per_cpu_offset(i);
if ((addr >= start) && (addr < end))
--
-
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