Merging upstream version 4.19.304.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 41 insertions, 27 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 98abff046..b43d681b0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2209,8 +2209,11 @@ void trace_buffered_event_enable(void)
 	for_each_tracing_cpu(cpu) {
 		page = alloc_pages_node(cpu_to_node(cpu),
 					GFP_KERNEL | __GFP_NORETRY, 0);
-		if (!page)
-			goto failed;
+		/* This is just an optimization and can handle failures */
+		if (!page) {
+			pr_err("Failed to allocate event buffer\n");
+			break;
+		}
 
 		event = page_address(page);
 		memset(event, 0, sizeof(*event));
@@ -2224,10 +2227,6 @@ void trace_buffered_event_enable(void)
 			WARN_ON_ONCE(1);
 		preempt_enable();
 	}
-
-	return;
- failed:
-	trace_buffered_event_disable();
 }
 
 static void enable_trace_buffered_event(void *data)
@@ -2262,11 +2261,9 @@ void trace_buffered_event_disable(void)
 	if (--trace_buffered_event_ref)
 		return;
 
-	preempt_disable();
 	/* For each CPU, set the buffer as used. */
-	smp_call_function_many(tracing_buffer_mask,
-			       disable_trace_buffered_event, NULL, 1);
-	preempt_enable();
+	on_each_cpu_mask(tracing_buffer_mask, disable_trace_buffered_event,
+			 NULL, true);
 
 	/* Wait for all current users to finish */
 	synchronize_sched();
@@ -2275,17 +2272,19 @@ void trace_buffered_event_disable(void)
 		free_page((unsigned long)per_cpu(trace_buffered_event, cpu));
 		per_cpu(trace_buffered_event, cpu) = NULL;
 	}
+
 	/*
-	 * Make sure trace_buffered_event is NULL before clearing
-	 * trace_buffered_event_cnt.
+	 * Wait for all CPUs that potentially started checking if they can use
+	 * their event buffer only after the previous synchronize_rcu() call and
+	 * they still read a valid pointer from trace_buffered_event. It must be
+	 * ensured they don't see cleared trace_buffered_event_cnt else they
+	 * could wrongly decide to use the pointed-to buffer which is now freed.
 	 */
-	smp_wmb();
+	synchronize_rcu();
 
-	preempt_disable();
-	/* Do the work on each cpu */
-	smp_call_function_many(tracing_buffer_mask,
-			       enable_trace_buffered_event, NULL, 1);
-	preempt_enable();
+	/* For each CPU, relinquish the buffer */
+	on_each_cpu_mask(tracing_buffer_mask, enable_trace_buffered_event, NULL,
+			 true);
 }
 
 static struct ring_buffer *temp_buffer;
@@ -3277,8 +3276,15 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 	 * will point to the same string as current_trace->name.
 	 */
 	mutex_lock(&trace_types_lock);
-	if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name))
+	if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) {
+		/* Close iter->trace before switching to the new current tracer */
+		if (iter->trace->close)
+			iter->trace->close(iter);
 		*iter->trace = *tr->current_trace;
+		/* Reopen the new current tracer */
+		if (iter->trace->open)
+			iter->trace->open(iter);
+	}
 	mutex_unlock(&trace_types_lock);
 
 #ifdef CONFIG_TRACER_MAX_TRACE
@@ -5252,8 +5258,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
 		return ret;
 
 #ifdef CONFIG_TRACER_MAX_TRACE
-	if (!(tr->flags & TRACE_ARRAY_FL_GLOBAL) ||
-	    !tr->current_trace->use_max_tr)
+	if (!tr->current_trace->use_max_tr)
 		goto out;
 
 	ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu);
@@ -7107,14 +7112,23 @@ static ssize_t
 tracing_read_dyn_info(struct file *filp, char __user *ubuf,
 		  size_t cnt, loff_t *ppos)
 {
-	unsigned long *p = filp->private_data;
-	char buf[64]; /* Not too big for a shallow stack */
+	ssize_t ret;
+	char *buf;
 	int r;
 
-	r = scnprintf(buf, 63, "%ld", *p);
-	buf[r++] = '\n';
+	/* 256 should be plenty to hold the amount needed */
+	buf = kmalloc(256, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	r = scnprintf(buf, 256, "%ld pages:%ld groups: %ld\n",
+		      ftrace_update_tot_cnt,
+		      ftrace_number_of_pages,
+		      ftrace_number_of_groups);
 
-	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+	ret = simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+	kfree(buf);
+	return ret;
 }
 
 static const struct file_operations tracing_dyn_info_fops = {
@@ -8246,7 +8260,7 @@ static __init int tracer_init_tracefs(void)
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 	trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
-			&ftrace_update_tot_cnt, &tracing_dyn_info_fops);
+			NULL, &tracing_dyn_info_fops);
 #endif
 
 	create_trace_instances(d_tracer);