[V3,00/29] stacktrace: Consolidate stack trace usage
diff mbox

Message ID 20190425094453.875139013@linutronix.de
State New
Headers show

Commit Message

Thomas Gleixner April 25, 2019, 9:44 a.m. UTC
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<-------------

Comments

Ingo Molnar April 25, 2019, 10:09 a.m. UTC | #1
* Thomas Gleixner <tglx@linutronix.de> wrote:

> -	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);

Just a minor style nit: the 'else' should probably on the same line as 
the '}' it belongs to, to make it really obvious that the 'if' has an 
'else' branch?

At that point the condition should probably also use balanced curly 
braces.

Interdiff looks good otherwise.

Thanks,

	Ingo
Josh Poimboeuf April 25, 2019, 1:31 p.m. UTC | #2
On Thu, Apr 25, 2019 at 11:44:53AM +0200, Thomas Gleixner wrote:
> 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

Other than the 2 minor nits:

Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

Patch
diff mbox

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,