From: "Steven Rostedt (Google)" <[email protected]>
In preparation for having the ring buffer mapped to a dedicated location,
which will have the same restrictions as user space memory mapped buffers,
allow it to use the "mapped" field of the ring_buffer_per_cpu structure
without having the user space meta page mapping.
When this starts using the mapped field, it will need to handle adding a
user space mapping (and removing it) from a ring buffer that is using a
dedicated memory range.
Signed-off-by: Steven Rostedt (Google) <[email protected]>
---
kernel/trace/ring_buffer.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 28853966aa9a..78beaccf9c8c 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -5224,6 +5224,9 @@ static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct trace_buffer_meta *meta = cpu_buffer->meta_page;
+ if (!meta)
+ return;
+
meta->reader.read = cpu_buffer->reader_page->read;
meta->reader.id = cpu_buffer->reader_page->id;
meta->reader.lost_events = cpu_buffer->lost_events;
@@ -6167,7 +6170,7 @@ rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu)
mutex_lock(&cpu_buffer->mapping_lock);
- if (!cpu_buffer->mapped) {
+ if (!cpu_buffer->mapped || !cpu_buffer->meta_page) {
mutex_unlock(&cpu_buffer->mapping_lock);
return ERR_PTR(-ENODEV);
}
@@ -6359,12 +6362,13 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu,
*/
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
+
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
err = __rb_map_vma(cpu_buffer, vma);
if (!err) {
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
- cpu_buffer->mapped = 1;
+ cpu_buffer->mapped++;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
} else {
kfree(cpu_buffer->subbuf_ids);
@@ -6403,7 +6407,8 @@ int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
mutex_lock(&buffer->mutex);
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
- cpu_buffer->mapped = 0;
+ WARN_ON_ONCE(!cpu_buffer->mapped);
+ cpu_buffer->mapped--;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
--
2.43.0