Merge tag 'v4.9.242' of git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable into odroidg12-4.9.y

This is the 4.9.242 stable release

kernel/debug/debug_core.c

@@ -94,14 +94,6 @@ int dbg_switch_cpu;
 /* Use kdb or gdbserver mode */
 int dbg_kdb_mode = 1;
 
-static int __init opt_kgdb_con(char *str)
-{
-	kgdb_use_con = 1;
-	return 0;
-}
-
-early_param("kgdbcon", opt_kgdb_con);
-
 module_param(kgdb_use_con, int, 0644);
 module_param(kgdbreboot, int, 0644);
 
@@ -811,6 +803,20 @@ static struct console kgdbcons = {
 	.index		= -1,
 };
 
+static int __init opt_kgdb_con(char *str)
+{
+	kgdb_use_con = 1;
+
+	if (kgdb_io_module_registered && !kgdb_con_registered) {
+		register_console(&kgdbcons);
+		kgdb_con_registered = 1;
+	}
+
+	return 0;
+}
+
+early_param("kgdbcon", opt_kgdb_con);
+
 #ifdef CONFIG_MAGIC_SYSRQ
 static void sysrq_handle_dbg(int key)
 {

kernel/fork.c

@@ -1756,14 +1756,9 @@ static __latent_entropy struct task_struct *copy_process(
 	/* ok, now we should be set up.. */
 	p->pid = pid_nr(pid);
 	if (clone_flags & CLONE_THREAD) {
-		p->exit_signal = -1;
 		p->group_leader = current->group_leader;
 		p->tgid = current->tgid;
 	} else {
-		if (clone_flags & CLONE_PARENT)
-			p->exit_signal = current->group_leader->exit_signal;
-		else
-			p->exit_signal = (clone_flags & CSIGNAL);
 		p->group_leader = p;
 		p->tgid = p->pid;
 	}
@@ -1808,9 +1803,14 @@ static __latent_entropy struct task_struct *copy_process(
 	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
 		p->real_parent = current->real_parent;
 		p->parent_exec_id = current->parent_exec_id;
+		if (clone_flags & CLONE_THREAD)
+			p->exit_signal = -1;
+		else
+			p->exit_signal = current->group_leader->exit_signal;
 	} else {
 		p->real_parent = current;
 		p->parent_exec_id = current->self_exec_id;
+		p->exit_signal = (clone_flags & CSIGNAL);
 	}
 
 	spin_lock(&current->sighand->siglock);

kernel/kthread.c

@@ -828,7 +828,8 @@ void kthread_delayed_work_timer_fn(unsigned long __data)
 	/* Move the work from worker->delayed_work_list. */
 	WARN_ON_ONCE(list_empty(&work->node));
 	list_del_init(&work->node);
-	kthread_insert_work(worker, work, &worker->work_list);
+	if (!work->canceling)
+		kthread_insert_work(worker, work, &worker->work_list);
 
 	spin_unlock(&worker->lock);
 }

kernel/trace/ring_buffer.c

@@ -1650,18 +1650,18 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
 	unsigned long nr_pages;
-	int cpu, err = 0;
+	int cpu, err;
 
 	/*
 	 * Always succeed at resizing a non-existent buffer:
 	 */
 	if (!buffer)
-		return size;
+		return 0;
 
 	/* Make sure the requested buffer exists */
 	if (cpu_id != RING_BUFFER_ALL_CPUS &&
 	    !cpumask_test_cpu(cpu_id, buffer->cpumask))
-		return size;
+		return 0;
 
 	nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
 
@@ -1801,7 +1801,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
 	}
 
 	mutex_unlock(&buffer->mutex);
-	return size;
+	return 0;
 
  out_err:
 	for_each_buffer_cpu(buffer, cpu) {

kernel/trace/trace.c

@@ -2403,7 +2403,7 @@ static char *get_trace_buf(void)
 
 	/* Interrupts must see nesting incremented before we use the buffer */
 	barrier();
-	return &buffer->buffer[buffer->nesting][0];
+	return &buffer->buffer[buffer->nesting - 1][0];
 }
 
 static void put_trace_buf(void)

kernel/trace/trace.h

@@ -491,6 +491,12 @@ enum {
  * can only be modified by current, we can reuse trace_recursion.
  */
 	TRACE_IRQ_BIT,
+
+	/*
+	 * When transitioning between context, the preempt_count() may
+	 * not be correct. Allow for a single recursion to cover this case.
+	 */
+	TRACE_TRANSITION_BIT,
 };
 
 #define trace_recursion_set(bit)	do { (current)->trace_recursion |= (1<<(bit)); } while (0)
@@ -535,14 +541,27 @@ static __always_inline int trace_test_and_set_recursion(int start, int max)
 		return 0;
 
 	bit = trace_get_context_bit() + start;
-	if (unlikely(val & (1 << bit)))
-		return -1;
+	if (unlikely(val & (1 << bit))) {
+		/*
+		 * It could be that preempt_count has not been updated during
+		 * a switch between contexts. Allow for a single recursion.
+		 */
+		bit = TRACE_TRANSITION_BIT;
+		if (trace_recursion_test(bit))
+			return -1;
+		trace_recursion_set(bit);
+		barrier();
+		return bit + 1;
+	}
+
+	/* Normal check passed, clear the transition to allow it again */
+	trace_recursion_clear(TRACE_TRANSITION_BIT);
 
 	val |= 1 << bit;
 	current->trace_recursion = val;
 	barrier();
 
-	return bit;
+	return bit + 1;
 }
 
 static __always_inline void trace_clear_recursion(int bit)
@@ -552,6 +571,7 @@ static __always_inline void trace_clear_recursion(int bit)
 	if (!bit)
 		return;
 
+	bit--;
 	bit = 1 << bit;
 	val &= ~bit;
 

kernel/trace/trace_selftest.c

@@ -490,8 +490,13 @@ trace_selftest_function_recursion(void)
 	unregister_ftrace_function(&test_rec_probe);
 
 	ret = -1;
-	if (trace_selftest_recursion_cnt != 1) {
-		pr_cont("*callback not called once (%d)* ",
+	/*
+	 * Recursion allows for transitions between context,
+	 * and may call the callback twice.
+	 */
+	if (trace_selftest_recursion_cnt != 1 &&
+	    trace_selftest_recursion_cnt != 2) {
+		pr_cont("*callback not called once (or twice) (%d)* ",
 			trace_selftest_recursion_cnt);
 		goto out;
 	}