unsigned long nr_stack_trace_entries;
#ifdef CONFIG_PROVE_LOCKING
+/**
+ * struct lock_trace - single stack backtrace
+ * @hash_entry: Entry in a stack_trace_hash[] list.
+ * @hash: jhash() of @entries.
+ * @nr_entries: Number of entries in @entries.
+ * @entries: Actual stack backtrace.
+ */
+struct lock_trace {
+ struct hlist_node hash_entry;
+ u32 hash;
+ u32 nr_entries;
+ unsigned long entries[0] __aligned(sizeof(unsigned long));
+};
+#define LOCK_TRACE_SIZE_IN_LONGS \
+ (sizeof(struct lock_trace) / sizeof(unsigned long))
/*
- * Stack-trace: tightly packed array of stack backtrace
- * addresses. Protected by the graph_lock.
+ * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
*/
static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
+static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
+
+static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
+{
+ return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
+ memcmp(t1->entries, t2->entries,
+ t1->nr_entries * sizeof(t1->entries[0])) == 0;
+}
-static int save_trace(struct lock_trace *trace)
+static struct lock_trace *save_trace(void)
{
- unsigned long *entries = stack_trace + nr_stack_trace_entries;
+ struct lock_trace *trace, *t2;
+ struct hlist_head *hash_head;
+ u32 hash;
unsigned int max_entries;
- trace->offset = nr_stack_trace_entries;
- max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
- trace->nr_entries = stack_trace_save(entries, max_entries, 3);
- nr_stack_trace_entries += trace->nr_entries;
+ BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
+ BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
+
+ trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
+ max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
+ LOCK_TRACE_SIZE_IN_LONGS;
+ trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
- if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
+ if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES -
+ LOCK_TRACE_SIZE_IN_LONGS - 1) {
if (!debug_locks_off_graph_unlock())
- return 0;
+ return NULL;
print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
dump_stack();
- return 0;
+ return NULL;
}
- return 1;
+ hash = jhash(trace->entries, trace->nr_entries *
+ sizeof(trace->entries[0]), 0);
+ trace->hash = hash;
+ hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
+ hlist_for_each_entry(t2, hash_head, hash_entry) {
+ if (traces_identical(trace, t2))
+ return t2;
+ }
+ nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
+ hlist_add_head(&trace->hash_entry, hash_head);
+
+ return trace;
}
#endif
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 lock_trace *trace)
+ const struct lock_trace *trace)
{
struct lock_list *entry;
/*
entry->class = this;
entry->links_to = links_to;
entry->distance = distance;
- entry->trace = *trace;
+ entry->trace = trace;
/*
* Both allocation and removal are done under the graph lock; but
* iteration is under RCU-sched; see look_up_lock_class() and
}
-static void print_lock_trace(struct lock_trace *trace, unsigned int spaces)
+static void print_lock_trace(const struct lock_trace *trace,
+ unsigned int spaces)
{
- unsigned long *entries = stack_trace + trace->offset;
-
- stack_trace_print(entries, trace->nr_entries, spaces);
+ stack_trace_print(trace->entries, trace->nr_entries, spaces);
}
/*
printk("\n-> #%u", depth);
print_lock_name(target->class);
printk(KERN_CONT ":\n");
- print_lock_trace(&target->trace, 6);
+ print_lock_trace(target->trace, 6);
}
static void
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
- if (!save_trace(&this->trace))
+ this->trace = save_trace();
+ if (!this->trace)
return;
depth = get_lock_depth(target);
*/
static noinline int
check_noncircular(struct held_lock *src, struct held_lock *target,
- struct lock_trace *trace)
+ struct lock_trace **const trace)
{
int ret;
struct lock_list *uninitialized_var(target_entry);
ret = check_path(hlock_class(target), &src_entry, &target_entry);
if (unlikely(!ret)) {
- if (!trace->nr_entries) {
+ if (!*trace) {
/*
* If save_trace fails here, the printing might
* trigger a WARN but because of the !nr_entries it
* should not do bad things.
*/
- save_trace(trace);
+ *trace = save_trace();
}
print_circular_bug(&src_entry, target_entry, src, target);
len += printk("%*s %s", depth, "", usage_str[bit]);
len += printk(KERN_CONT " at:\n");
- print_lock_trace(class->usage_traces + bit, len);
+ print_lock_trace(class->usage_traces[bit], len);
}
}
printk("%*s }\n", depth, "");
do {
print_lock_class_header(entry->class, depth);
printk("%*s ... acquired at:\n", depth, "");
- print_lock_trace(&entry->trace, 2);
+ print_lock_trace(entry->trace, 2);
printk("\n");
if (depth == 0 && (entry != root)) {
print_lock_name(backwards_entry->class);
pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
- print_lock_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_lock_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,
lockdep_print_held_locks(curr);
pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
- if (!save_trace(&prev_root->trace))
+ prev_root->trace = save_trace();
+ if (!prev_root->trace)
return;
print_shortest_lock_dependencies(backwards_entry, prev_root);
pr_warn("\nthe dependencies between the lock to be acquired");
pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
- if (!save_trace(&next_root->trace))
+ next_root->trace = save_trace();
+ if (!next_root->trace)
return;
print_shortest_lock_dependencies(forwards_entry, next_root);
*/
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next, int distance, struct lock_trace *trace)
+ struct held_lock *next, int distance,
+ struct lock_trace **const trace)
{
struct lock_list *entry;
int ret;
return ret;
#endif
- if (!trace->nr_entries && !save_trace(trace))
- return 0;
+ if (!*trace) {
+ *trace = save_trace();
+ if (!*trace)
+ return 0;
+ }
/*
* Ok, all validations passed, add the new lock
*/
ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
&hlock_class(prev)->locks_after,
- next->acquire_ip, distance, trace);
+ next->acquire_ip, distance, *trace);
if (!ret)
return 0;
ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
&hlock_class(next)->locks_before,
- next->acquire_ip, distance, trace);
+ next->acquire_ip, distance, *trace);
if (!ret)
return 0;
static int
check_prevs_add(struct task_struct *curr, struct held_lock *next)
{
- struct lock_trace trace = { .nr_entries = 0 };
+ struct lock_trace *trace = NULL;
int depth = curr->lockdep_depth;
struct held_lock *hlock;
print_lock(this);
pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
- print_lock_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");
lockdep_print_held_locks(curr);
pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
- if (!save_trace(&root->trace))
+ root->trace = save_trace();
+ if (!root->trace)
return;
print_shortest_lock_dependencies(other, root);
hlock_class(this)->usage_mask |= new_mask;
- if (!save_trace(hlock_class(this)->usage_traces + new_bit))
+ if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
return 0;
switch (new_bit) {
) / 1024
);
+#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
+ printk(" memory used for stack traces: %zu kB\n",
+ (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
+ );
+#endif
+
printk(" per task-struct memory footprint: %zu bytes\n",
sizeof(((struct task_struct *)NULL)->held_locks));
}
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