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Subject[patch V3 00/29] stacktrace: Consolidate stack trace usage
This is an update to V2 which can be found here:

https://lkml.kernel.org/r/20190418084119.056416939@linutronix.de

Changes vs. V2:

- Fixed the kernel-doc issue pointed out by Mike

- Removed the '-1' oddity from the tracer

- Restricted the tracer nesting to 4

- Restored the lockdep magic to prevent redundant stack traces

- Addressed the small nitpicks here and there

- Picked up Acked/Reviewed tags

The series is based on:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core/stacktrace

which contains the removal of the inconsistent and pointless ULONG_MAX
termination of stacktraces.

It's also available from git:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.core/stacktrace

up to 5160eb663575 ("x86/stacktrace: Use common infrastructure")

Delta patch vs. v2 below.

Thanks,

tglx

8<-------------
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 654949dc1c16..f0cfd12cb45e 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -32,14 +32,13 @@ unsigned int stack_trace_save_user(unsigned long *store, unsigned int size);
* @reliable: True when the stack entry is reliable. Required by
* some printk based consumers.
*
- * Returns: True, if the entry was consumed or skipped
+ * Return: True, if the entry was consumed or skipped
* False, if there is no space left to store
*/
typedef bool (*stack_trace_consume_fn)(void *cookie, unsigned long addr,
bool reliable);
/**
* arch_stack_walk - Architecture specific function to walk the stack
-
* @consume_entry: Callback which is invoked by the architecture code for
* each entry.
* @cookie: Caller supplied pointer which is handed back to
@@ -47,10 +46,12 @@ typedef bool (*stack_trace_consume_fn)(void *cookie, unsigned long addr,
* @task: Pointer to a task struct, can be NULL
* @regs: Pointer to registers, can be NULL
*
- * @task @regs:
- * NULL NULL Stack trace from current
+ * ============ ======= ============================================
+ * task regs
+ * ============ ======= ============================================
* task NULL Stack trace from task (can be current)
- * NULL regs Stack trace starting on regs->stackpointer
+ * current regs Stack trace starting on regs->stackpointer
+ * ============ ======= ============================================
*/
void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
struct task_struct *task, struct pt_regs *regs);
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 1e8e246edaad..badd77670d00 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -705,7 +705,8 @@ static struct dma_debug_entry *dma_entry_alloc(void)

#ifdef CONFIG_STACKTRACE
entry->stack_len = stack_trace_save(entry->stack_entries,
- ARRAY_SIZE(entry->stack_entries), 1);
+ ARRAY_SIZE(entry->stack_entries),
+ 1);
#endif
return entry;
}
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 84423f0bb0b0..45bcaf2e4cb6 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2160,12 +2160,11 @@ check_deadlock(struct task_struct *curr, struct held_lock *next,
*/
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
- struct held_lock *next, int distance)
+ struct held_lock *next, int distance, struct lock_trace *trace)
{
struct lock_list *uninitialized_var(target_entry);
struct lock_list *entry;
struct lock_list this;
- struct lock_trace trace;
int ret;

if (!hlock_class(prev)->key || !hlock_class(next)->key) {
@@ -2198,8 +2197,17 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
this.class = hlock_class(next);
this.parent = NULL;
ret = check_noncircular(&this, hlock_class(prev), &target_entry);
- if (unlikely(!ret))
+ if (unlikely(!ret)) {
+ if (!trace->nr_entries) {
+ /*
+ * 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);
+ }
return print_circular_bug(&this, target_entry, next, prev);
+ }
else if (unlikely(ret < 0))
return print_bfs_bug(ret);

@@ -2246,7 +2254,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
return print_bfs_bug(ret);


- if (!save_trace(&trace))
+ if (!trace->nr_entries && !save_trace(trace))
return 0;

/*
@@ -2255,14 +2263,14 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
*/
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;

@@ -2278,6 +2286,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
static int
check_prevs_add(struct task_struct *curr, struct held_lock *next)
{
+ struct lock_trace trace = { .nr_entries = 0 };
int depth = curr->lockdep_depth;
struct held_lock *hlock;

@@ -2305,8 +2314,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
* added:
*/
if (hlock->read != 2 && hlock->check) {
- int ret = check_prev_add(curr, hlock, next, distance);
-
+ int ret = check_prev_add(curr, hlock, next, distance,
+ &trace);
if (!ret)
return 0;

diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 26cc92288cfb..27bafc1e271e 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -39,6 +39,8 @@ EXPORT_SYMBOL_GPL(stack_trace_print);
* @entries: Pointer to storage array
* @nr_entries: Number of entries in the storage array
* @spaces: Number of leading spaces to print
+ *
+ * Return: Number of bytes printed.
*/
int stack_trace_snprint(char *buf, size_t size, unsigned long *entries,
unsigned int nr_entries, int spaces)
@@ -48,7 +50,7 @@ int stack_trace_snprint(char *buf, size_t size, unsigned long *entries,
if (WARN_ON(!entries))
return 0;

- for (i = 0; i < nr_entries; i++) {
+ for (i = 0; i < nr_entries && size; i++) {
generated = snprintf(buf, size, "%*c%pS\n", 1 + spaces, ' ',
(void *)entries[i]);

@@ -105,7 +107,7 @@ static bool stack_trace_consume_entry_nosched(void *cookie, unsigned long addr,
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
*
- * Returns number of entries stored.
+ * Return: Number of trace entries stored.
*/
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
unsigned int skipnr)
@@ -129,7 +131,7 @@ EXPORT_SYMBOL_GPL(stack_trace_save);
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
*
- * Returns number of entries stored.
+ * Return: Number of trace entries stored.
*/
unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
unsigned int size, unsigned int skipnr)
@@ -156,7 +158,7 @@ unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
*
- * Returns number of entries stored.
+ * Return: Number of trace entries stored.
*/
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
unsigned int size, unsigned int skipnr)
@@ -179,7 +181,7 @@ unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
* @store: Pointer to storage array
* @size: Size of the storage array
*
- * Returns: An error if it detects any unreliable features of the
+ * Return: An error if it detects any unreliable features of the
* stack. Otherwise it guarantees that the stack trace is
* reliable and returns the number of entries stored.
*
@@ -214,7 +216,7 @@ int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
* @store: Pointer to storage array
* @size: Size of the storage array
*
- * Returns number of entries stored.
+ * Return: Number of trace entries stored.
*/
unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
{
@@ -265,6 +267,8 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk,
* @store: Pointer to storage array
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
+ *
+ * Return: Number of trace entries stored
*/
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
unsigned int skipnr)
@@ -286,6 +290,8 @@ EXPORT_SYMBOL_GPL(stack_trace_save);
* @store: Pointer to storage array
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
+ *
+ * Return: Number of trace entries stored
*/
unsigned int stack_trace_save_tsk(struct task_struct *task,
unsigned long *store, unsigned int size,
@@ -307,6 +313,8 @@ unsigned int stack_trace_save_tsk(struct task_struct *task,
* @store: Pointer to storage array
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
+ *
+ * Return: Number of trace entries stored
*/
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
unsigned int size, unsigned int skipnr)
@@ -328,7 +336,7 @@ unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
* @store: Pointer to storage array
* @size: Size of the storage array
*
- * Returns: An error if it detects any unreliable features of the
+ * Return: An error if it detects any unreliable features of the
* stack. Otherwise it guarantees that the stack trace is
* reliable and returns the number of entries stored.
*
@@ -352,6 +360,8 @@ int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
* stack_trace_save_user - Save a user space stack trace into a storage array
* @store: Pointer to storage array
* @size: Size of the storage array
+ *
+ * Return: Number of trace entries stored
*/
unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
{
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4b6d3e0ebd41..dd00ed3a9473 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2751,15 +2751,15 @@ trace_function(struct trace_array *tr,

#ifdef CONFIG_STACKTRACE

-/* 64 entries for kernel stacks are plenty */
-#define FTRACE_KSTACK_ENTRIES 64
+/* Allow 4 levels of nesting: normal, softirq, irq, NMI */
+#define FTRACE_KSTACK_NESTING 4
+
+#define FTRACE_KSTACK_ENTRIES (PAGE_SIZE / FTRACE_KSTACK_NESTING)

struct ftrace_stack {
unsigned long calls[FTRACE_KSTACK_ENTRIES];
};

-/* This allows 8 level nesting which is plenty */
-#define FTRACE_KSTACK_NESTING (PAGE_SIZE / sizeof(struct ftrace_stack))

struct ftrace_stacks {
struct ftrace_stack stacks[FTRACE_KSTACK_NESTING];
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 2fc137f0ee24..031f78b35bae 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -394,7 +394,8 @@ stack_trace_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
- int ret, was_enabled;
+ int was_enabled;
+ int ret;

mutex_lock(&stack_sysctl_mutex);
was_enabled = !!stack_tracer_enabled;
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 5936e20cd0a6..605c61f65d94 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -197,7 +197,11 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
/**
* stack_depot_fetch - Fetch stack entries from a depot
*
+ * @handle: Stack depot handle which was returned from
+ * stack_depot_save().
* @entries: Pointer to store the entries address
+ *
+ * Return: The number of trace entries for this depot.
*/
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries)
@@ -219,7 +223,7 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch);
* @nr_entries: Size of the storage array
* @alloc_flags: Allocation gfp flags
*
- * Returns the handle of the stack struct stored in depot
+ * Return: The handle of the stack struct stored in depot
*/
depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
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