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authorLinus Torvalds <torvalds@linux-foundation.org>2017-04-20 12:30:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-04-20 12:30:10 -0700
commit160062e19001b224370cddeaf652f258fd916fb0 (patch)
treede1e9fc6f241141a9a5960b170b774841152e2b1
parent7f425895926af100cfdaebd504703325e5c08d3c (diff)
parent78f7a45dac2a2d2002f98a3a95f7979867868d73 (diff)
Merge tag 'trace-v4.11-rc5-5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull two more ftrace fixes from Steven Rostedt: "While continuing my development, I uncovered two more small bugs. One is a race condition when enabling the snapshot function probe trigger. It enables the probe before allocating the snapshot, and if the probe triggers first, it stops tracing with a warning that the snapshot buffer was not allocated. The seconds is that the snapshot file should show how to use it when it is empty. But a bug fix from long ago broke the "is empty" test and the snapshot file no longer displays the help message" * tag 'trace-v4.11-rc5-5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: ring-buffer: Have ring_buffer_iter_empty() return true when empty tracing: Allocate the snapshot buffer before enabling probe
-rw-r--r--kernel/trace/ring_buffer.c16
-rw-r--r--kernel/trace/trace.c8
2 files changed, 19 insertions, 5 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 54e7a90db848..ca47a4fa2986 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3405,11 +3405,23 @@ EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ struct buffer_page *reader;
+ struct buffer_page *head_page;
+ struct buffer_page *commit_page;
+ unsigned commit;
cpu_buffer = iter->cpu_buffer;
- return iter->head_page == cpu_buffer->commit_page &&
- iter->head == rb_commit_index(cpu_buffer);
+ /* Remember, trace recording is off when iterator is in use */
+ reader = cpu_buffer->reader_page;
+ head_page = cpu_buffer->head_page;
+ commit_page = cpu_buffer->commit_page;
+ commit = rb_page_commit(commit_page);
+
+ return ((iter->head_page == commit_page && iter->head == commit) ||
+ (iter->head_page == reader && commit_page == head_page &&
+ head_page->read == commit &&
+ iter->head == rb_page_commit(cpu_buffer->reader_page)));
}
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d484452ae648..0ad75e9698f6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6733,11 +6733,13 @@ ftrace_trace_snapshot_callback(struct ftrace_hash *hash,
return ret;
out_reg:
- ret = register_ftrace_function_probe(glob, ops, count);
+ ret = alloc_snapshot(&global_trace);
+ if (ret < 0)
+ goto out;
- if (ret >= 0)
- alloc_snapshot(&global_trace);
+ ret = register_ftrace_function_probe(glob, ops, count);
+ out:
return ret < 0 ? ret : 0;
}