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Subject[patch V3 01/29] tracing: Cleanup stack trace code
- Remove the extra array member of stack_dump_trace[] along with the
ARRAY_SIZE - 1 initialization for struct stack_trace :: max_entries.

Both are historical leftovers of no value. The stack tracer never exceeds
the array and there is no extra storage requirement either.

- Make variables which are only used in trace_stack.c static.

- Simplify the enable/disable logic.

- Rename stack_trace_print() as it's using the stack_trace_ namespace. Free
the name up for stack trace related functions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
---
V3: Remove the -1 init and split the variable declaration as requested by Steven.
V2: Add more cleanups and use print_max_stack() as requested by Steven.
---
include/linux/ftrace.h | 18 ++++--------------
kernel/trace/trace_stack.c | 42 +++++++++++++-----------------------------
2 files changed, 17 insertions(+), 43 deletions(-)

--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -241,21 +241,11 @@ static inline void ftrace_free_mem(struc

#ifdef CONFIG_STACK_TRACER

-#define STACK_TRACE_ENTRIES 500
-
-struct stack_trace;
-
-extern unsigned stack_trace_index[];
-extern struct stack_trace stack_trace_max;
-extern unsigned long stack_trace_max_size;
-extern arch_spinlock_t stack_trace_max_lock;
-
extern int stack_tracer_enabled;
-void stack_trace_print(void);
-int
-stack_trace_sysctl(struct ctl_table *table, int write,
- void __user *buffer, size_t *lenp,
- loff_t *ppos);
+
+int stack_trace_sysctl(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos);

/* DO NOT MODIFY THIS VARIABLE DIRECTLY! */
DECLARE_PER_CPU(int, disable_stack_tracer);
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -18,30 +18,26 @@

#include "trace.h"

-static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES + 1];
-unsigned stack_trace_index[STACK_TRACE_ENTRIES];
+#define STACK_TRACE_ENTRIES 500
+
+static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];
+static unsigned stack_trace_index[STACK_TRACE_ENTRIES];

-/*
- * Reserve one entry for the passed in ip. This will allow
- * us to remove most or all of the stack size overhead
- * added by the stack tracer itself.
- */
struct stack_trace stack_trace_max = {
- .max_entries = STACK_TRACE_ENTRIES - 1,
+ .max_entries = STACK_TRACE_ENTRIES,
.entries = &stack_dump_trace[0],
};

-unsigned long stack_trace_max_size;
-arch_spinlock_t stack_trace_max_lock =
+static unsigned long stack_trace_max_size;
+static arch_spinlock_t stack_trace_max_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

DEFINE_PER_CPU(int, disable_stack_tracer);
static DEFINE_MUTEX(stack_sysctl_mutex);

int stack_tracer_enabled;
-static int last_stack_tracer_enabled;

-void stack_trace_print(void)
+static void print_max_stack(void)
{
long i;
int size;
@@ -61,16 +57,7 @@ void stack_trace_print(void)
}
}

-/*
- * When arch-specific code overrides this function, the following
- * data should be filled up, assuming stack_trace_max_lock is held to
- * prevent concurrent updates.
- * stack_trace_index[]
- * stack_trace_max
- * stack_trace_max_size
- */
-void __weak
-check_stack(unsigned long ip, unsigned long *stack)
+static void check_stack(unsigned long ip, unsigned long *stack)
{
unsigned long this_size, flags; unsigned long *p, *top, *start;
static int tracer_frame;
@@ -179,7 +166,7 @@ check_stack(unsigned long ip, unsigned l
stack_trace_max.nr_entries = x;

if (task_stack_end_corrupted(current)) {
- stack_trace_print();
+ print_max_stack();
BUG();
}

@@ -412,23 +399,21 @@ stack_trace_sysctl(struct ctl_table *tab
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
+ int was_enabled;
int ret;

mutex_lock(&stack_sysctl_mutex);
+ was_enabled = !!stack_tracer_enabled;

ret = proc_dointvec(table, write, buffer, lenp, ppos);

- if (ret || !write ||
- (last_stack_tracer_enabled == !!stack_tracer_enabled))
+ if (ret || !write || (was_enabled == !!stack_tracer_enabled))
goto out;

- last_stack_tracer_enabled = !!stack_tracer_enabled;
-
if (stack_tracer_enabled)
register_ftrace_function(&trace_ops);
else
unregister_ftrace_function(&trace_ops);
-
out:
mutex_unlock(&stack_sysctl_mutex);
return ret;
@@ -444,7 +429,6 @@ static __init int enable_stacktrace(char
strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);

stack_tracer_enabled = 1;
- last_stack_tracer_enabled = 1;
return 1;
}
__setup("stacktrace", enable_stacktrace);

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