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Subject[RFC patch 35/41] lockdep: Simplify stack trace handling
Replace the indirection through struct stack_trace by using the storage
array based interfaces and storing the information is a small lockdep
specific data structure.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/lockdep.h | 9 +++++++--
kernel/locking/lockdep.c | 39 ++++++++++++++++++++-------------------
2 files changed, 27 insertions(+), 21 deletions(-)

--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -66,6 +66,11 @@ struct lock_class_key {

extern struct lock_class_key __lockdep_no_validate__;

+struct lock_trace {
+ unsigned int nr_entries;
+ unsigned int offset;
+};
+
#define LOCKSTAT_POINTS 4

/*
@@ -100,7 +105,7 @@ struct lock_class {
* IRQ/softirq usage tracking bits:
*/
unsigned long usage_mask;
- struct stack_trace usage_traces[XXX_LOCK_USAGE_STATES];
+ struct lock_trace usage_traces[XXX_LOCK_USAGE_STATES];

/*
* Generation counter, when doing certain classes of graph walking,
@@ -188,7 +193,7 @@ struct lock_list {
struct list_head entry;
struct lock_class *class;
struct lock_class *links_to;
- struct stack_trace trace;
+ struct lock_trace trace;
int distance;

/*
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -434,18 +434,13 @@ static void print_lockdep_off(const char
#endif
}

-static int save_trace(struct stack_trace *trace)
+static int save_trace(struct lock_trace *trace)
{
- trace->nr_entries = 0;
- trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
- trace->entries = stack_trace + nr_stack_trace_entries;
-
- trace->skip = 3;
-
- save_stack_trace(trace);
-
- trace->max_entries = trace->nr_entries;
+ unsigned long *entries = stack_trace + nr_stack_trace_entries;
+ unsigned int nent = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;

+ trace->offset = nr_stack_trace_entries;
+ trace->nr_entries= stack_trace_save(entries, nent, 3);
nr_stack_trace_entries += trace->nr_entries;

if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
@@ -1196,7 +1191,7 @@ static struct lock_list *alloc_list_entr
static int add_lock_to_list(struct lock_class *this,
struct lock_class *links_to, struct list_head *head,
unsigned long ip, int distance,
- struct stack_trace *trace)
+ struct lock_trace *trace)
{
struct lock_list *entry;
/*
@@ -1415,6 +1410,13 @@ static inline int __bfs_backwards(struct
* checking.
*/

+static void print_lock_trace(struct lock_trace *trace, unsigned int spaces)
+{
+ unsigned long *entries = stack_trace + trace->offset;
+
+ stack_trace_print(entries, trace->nr_entries, spaces);
+}
+
/*
* Print a dependency chain entry (this is only done when a deadlock
* has been detected):
@@ -1427,8 +1429,7 @@ print_circular_bug_entry(struct lock_lis
printk("\n-> #%u", depth);
print_lock_name(target->class);
printk(KERN_CONT ":\n");
- print_stack_trace(&target->trace, 6);
-
+ print_lock_trace(&target->trace, 6);
return 0;
}

@@ -1740,7 +1741,7 @@ static void print_lock_class_header(stru

len += printk("%*s %s", depth, "", usage_str[bit]);
len += printk(KERN_CONT " at:\n");
- print_stack_trace(class->usage_traces + bit, len);
+ print_lock_trace(class->usage_traces + bit, len);
}
}
printk("%*s }\n", depth, "");
@@ -1765,7 +1766,7 @@ print_shortest_lock_dependencies(struct
do {
print_lock_class_header(entry->class, depth);
printk("%*s ... acquired at:\n", depth, "");
- print_stack_trace(&entry->trace, 2);
+ print_lock_trace(&entry->trace, 2);
printk("\n");

if (depth == 0 && (entry != root)) {
@@ -1878,14 +1879,14 @@ print_bad_irq_dependency(struct task_str
print_lock_name(backwards_entry->class);
pr_warn("\n... which became %s-irq-safe at:\n", irqclass);

- print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
+ print_lock_trace(backwards_entry->class->usage_traces + bit1, 1);

pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
print_lock_name(forwards_entry->class);
pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
pr_warn("...");

- print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
+ print_lock_trace(forwards_entry->class->usage_traces + bit2, 1);

pr_warn("\nother info that might help us debug this:\n\n");
print_irq_lock_scenario(backwards_entry, forwards_entry,
@@ -2161,9 +2162,9 @@ check_prev_add(struct task_struct *curr,
struct held_lock *next, int distance)
{
struct lock_list *uninitialized_var(target_entry);
- struct stack_trace trace;
struct lock_list *entry;
struct lock_list this;
+ struct lock_trace trace;
int ret;

if (!hlock_class(prev)->key || !hlock_class(next)->key) {
@@ -2801,7 +2802,7 @@ print_usage_bug(struct task_struct *curr
print_lock(this);

pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
- print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
+ print_lock_trace(hlock_class(this)->usage_traces + prev_bit, 1);

print_irqtrace_events(curr);
pr_warn("\nother info that might help us debug this:\n");

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