tracing fixes for v6.19:

- Remove useless assignment of soft_mode variable
 
   The function __ftrace_event_enable_disable() sets "soft_mode" in one of
   the branch paths but doesn't use it after that. Remove the setting of that
   variable.
 
 - Add a cond_resched() in ring_buffer_resize()
 
   The resize function that allocates all the pages for the ring buffer was
   causing a soft lockup on PREEMPT_NONE configs when allocating large
   buffers on machines with many CPUs. Hopefully this is the last
   cond_resched() needed to be added as PREEMPT_LAZY becomes the norm in the
   future.
 
 - Make ftrace_graph_ent depth field signed
 
   The "depth" field of struct ftrace_graph_ent was converted from "int" to
   "unsigned long" for alignment reasons to work with being embedded in other
   structures. The conversion from a signed to unsigned caused integrity
   checks to always pass as they were comparing "depth" to less than zero.
   Make the field signed long.
 
 - Add recursion protection to stack trace events
 
   A infinite recursion was triggered by a stack trace event calling RCU
   which internally called rcu_read_unlock_special(), which triggered an
   event that was also doing stacktraces which cause it to trigger the same
   RCU lock that called rcu_read_unlock_special() again.
 
   Update the trace_test_and_set_recursion() to add a set of context checks
   for events to use, and have the stack trace event use that for recursion
   protection.
 
 - Make the variable ftrace_dump_on_oops static
 
   The cleanup of sysctl that moved all the updates to the files that use
   them moved the reference of ftrace_dump_on_oops to where it is used.
   It is no longer used outside of the trace.c file. Make it static.
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Merge tag 'trace-v6.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fixes from Steven Rostedt:

 - Remove useless assignment of soft_mode variable

   The function __ftrace_event_enable_disable() sets "soft_mode" in one
   of the branch paths but doesn't use it after that. Remove the setting
   of that variable.

 - Add a cond_resched() in ring_buffer_resize()

   The resize function that allocates all the pages for the ring buffer
   was causing a soft lockup on PREEMPT_NONE configs when allocating
   large buffers on machines with many CPUs. Hopefully this is the last
   cond_resched() needed to be added as PREEMPT_LAZY becomes the norm in
   the future.

 - Make ftrace_graph_ent depth field signed

   The "depth" field of struct ftrace_graph_ent was converted from "int"
   to "unsigned long" for alignment reasons to work with being embedded
   in other structures. The conversion from a signed to unsigned caused
   integrity checks to always pass as they were comparing "depth" to
   less than zero. Make the field signed long.

 - Add recursion protection to stack trace events

   A infinite recursion was triggered by a stack trace event calling RCU
   which internally called rcu_read_unlock_special(), which triggered an
   event that was also doing stacktraces which cause it to trigger the
   same RCU lock that called rcu_read_unlock_special() again.

   Update the trace_test_and_set_recursion() to add a set of context
   checks for events to use, and have the stack trace event use that for
   recursion protection.

 - Make the variable ftrace_dump_on_oops static

   The cleanup of sysctl that moved all the updates to the files that
   use them moved the reference of ftrace_dump_on_oops to where it is
   used. It is no longer used outside of the trace.c file. Make it
   static.

* tag 'trace-v6.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  trace: ftrace_dump_on_oops[] is not exported, make it static
  tracing: Add recursion protection in kernel stack trace recording
  ftrace: Make ftrace_graph_ent depth field signed
  ring-buffer: Avoid softlockup in ring_buffer_resize() during memory free
  tracing: Drop unneeded assignment to soft_mode

include/linux/ftrace.h

@@ -1167,7 +1167,7 @@ static inline void ftrace_init(void) { }
  */
 struct ftrace_graph_ent {
 	unsigned long func; /* Current function */
-	unsigned long depth;
+	long depth; /* signed to check for less than zero */
 } __packed;
 
 /*

include/linux/trace_recursion.h

@@ -34,6 +34,13 @@ enum {
 	TRACE_INTERNAL_SIRQ_BIT,
 	TRACE_INTERNAL_TRANSITION_BIT,
 
+	/* Internal event use recursion bits */
+	TRACE_INTERNAL_EVENT_BIT,
+	TRACE_INTERNAL_EVENT_NMI_BIT,
+	TRACE_INTERNAL_EVENT_IRQ_BIT,
+	TRACE_INTERNAL_EVENT_SIRQ_BIT,
+	TRACE_INTERNAL_EVENT_TRANSITION_BIT,
+
 	TRACE_BRANCH_BIT,
 /*
  * Abuse of the trace_recursion.
@@ -58,6 +65,8 @@ enum {
 
 #define TRACE_LIST_START	TRACE_INTERNAL_BIT
 
+#define TRACE_EVENT_START	TRACE_INTERNAL_EVENT_BIT
+
 #define TRACE_CONTEXT_MASK	((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
 
 /*

kernel/trace/ring_buffer.c

@@ -3137,6 +3137,8 @@ int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
 					list) {
 			list_del_init(&bpage->list);
 			free_buffer_page(bpage);
+
+			cond_resched();
 		}
 	}
  out_err_unlock:

kernel/trace/trace.c

@@ -138,7 +138,7 @@ cpumask_var_t __read_mostly	tracing_buffer_mask;
  * by commas.
  */
 /* Set to string format zero to disable by default */
-char ftrace_dump_on_oops[MAX_TRACER_SIZE] = "0";
+static char ftrace_dump_on_oops[MAX_TRACER_SIZE] = "0";
 
 /* When set, tracing will stop when a WARN*() is hit */
 static int __disable_trace_on_warning;
@@ -3012,6 +3012,11 @@ static void __ftrace_trace_stack(struct trace_array *tr,
 	struct ftrace_stack *fstack;
 	struct stack_entry *entry;
 	int stackidx;
+	int bit;
+
+	bit = trace_test_and_set_recursion(_THIS_IP_, _RET_IP_, TRACE_EVENT_START);
+	if (bit < 0)
+		return;
 
 	/*
 	 * Add one, for this function and the call to save_stack_trace()
@@ -3080,6 +3085,7 @@ static void __ftrace_trace_stack(struct trace_array *tr,
 	/* Again, don't let gcc optimize things here */
 	barrier();
 	__this_cpu_dec(ftrace_stack_reserve);
+	trace_clear_recursion(bit);
 }
 
 static inline void ftrace_trace_stack(struct trace_array *tr,

kernel/trace/trace_events.c

@@ -826,16 +826,15 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
 		 * When soft_disable is set and enable is set, we want to
 		 * register the tracepoint for the event, but leave the event
 		 * as is. That means, if the event was already enabled, we do
-		 * nothing (but set soft_mode). If the event is disabled, we
-		 * set SOFT_DISABLED before enabling the event tracepoint, so
-		 * it still seems to be disabled.
+		 * nothing. If the event is disabled, we set SOFT_DISABLED
+		 * before enabling the event tracepoint, so it still seems
+		 * to be disabled.
 		 */
 		if (!soft_disable)
 			clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
 		else {
 			if (atomic_inc_return(&file->sm_ref) > 1)
 				break;
-			soft_mode = true;
 			/* Enable use of trace_buffered_event */
 			trace_buffered_event_enable();
 		}