[PATCH] percpu,lockdep: implement and use is_static_percpu_address()

From: Tejun Heo
Date: Tue Mar 09 2010 - 04:12:36 EST


lockdep has custom code to check whether a pointer belongs to static
percpu area which is somewhat broken. Implement proper
is_static_percpu_address() in percpu and replace the custom code.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
This wasn't the cause this time but I'll queue the fix in percpu tree
anyway.

Thanks.

include/linux/percpu.h | 7 +++++++
kernel/lockdep.c | 15 ++-------------
mm/percpu.c | 26 ++++++++++++++++++++++++++
3 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index a93e5bf..1eca064 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -137,6 +137,7 @@ extern int __init pcpu_page_first_chunk(size_t reserved_size,
extern void __percpu *__alloc_reserved_percpu(size_t size, size_t align);
extern void __percpu *__alloc_percpu(size_t size, size_t align);
extern void free_percpu(void __percpu *__pdata);
+extern bool is_static_percpu_address(unsigned long addr);
extern phys_addr_t per_cpu_ptr_to_phys(void *addr);

#ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
@@ -163,6 +164,12 @@ static inline void free_percpu(void __percpu *p)
kfree(p);
}

+/* can't distinguish from other static vars, always false */
+static inline bool is_static_percpu_address(unsigned long addr)
+{
+ return false;
+}
+
static inline phys_addr_t per_cpu_ptr_to_phys(void *addr)
{
return __pa(addr);
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 0c30d04..4206f6f 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -582,9 +582,6 @@ static int static_obj(void *obj)
unsigned long start = (unsigned long) &_stext,
end = (unsigned long) &_end,
addr = (unsigned long) obj;
-#ifdef CONFIG_SMP
- int i;
-#endif

/*
* static variable?
@@ -595,19 +592,11 @@ static int static_obj(void *obj)
if (arch_is_kernel_data(addr))
return 1;

-#ifdef CONFIG_SMP
/*
* 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
- + per_cpu_offset(i);
-
- if ((addr >= start) && (addr < end))
- return 1;
- }
-#endif
+ if (is_static_percpu_address(addr))
+ return 1;

/*
* module var?
diff --git a/mm/percpu.c b/mm/percpu.c
index 768419d..ae4d058 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1304,6 +1304,32 @@ void free_percpu(void __percpu *ptr)
EXPORT_SYMBOL_GPL(free_percpu);

/**
+ * is_static_percpu_address - test whether address is from static percpu area
+ * @addr: address to test
+ *
+ * Test whether @addr belongs to static percpu area. Module static
+ * percpu areas allocated via __alloc_reserved_percpu() is not
+ * considered. Use is_module_address() for those.
+ *
+ * RETURNS:
+ * %true if @addr is from static percpu area, %false otherwise.
+ */
+bool is_static_percpu_address(unsigned long addr)
+{
+ const size_t static_size = __per_cpu_end - __per_cpu_start;
+ void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
+ unsigned int cpu;
+
+ for_each_possible_cpu(cpu) {
+ void *start = per_cpu_ptr(base, cpu);
+
+ if ((void *)addr >= start && (void *)addr < start + static_size)
+ return true;
+ }
+ return false;
+}
+
+/**
* per_cpu_ptr_to_phys - convert translated percpu address to physical address
* @addr: the address to be converted to physical address
*
--
1.6.4.2

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