tracing: Fix traceon trigger condition to actually turn tracing on

[~andy/linux] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 815c878f409bd94e08777d1b9f83b1553f4a2e24..24c1f23825579df4f2bf46e2dca98e6af8fb4abd 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1600,15 +1600,31 @@ void trace_buffer_unlock_commit(struct ring_buffer *buffer,
 }
 EXPORT_SYMBOL_GPL(trace_buffer_unlock_commit);
 
+static struct ring_buffer *temp_buffer;
+
 struct ring_buffer_event *
 trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
                          struct ftrace_event_file *ftrace_file,
                          int type, unsigned long len,
                          unsigned long flags, int pc)
 {
+       struct ring_buffer_event *entry;
+
        *current_rb = ftrace_file->tr->trace_buffer.buffer;
-       return trace_buffer_lock_reserve(*current_rb,
+       entry = trace_buffer_lock_reserve(*current_rb,
                                         type, len, flags, pc);
+       /*
+        * If tracing is off, but we have triggers enabled
+        * we still need to look at the event data. Use the temp_buffer
+        * to store the trace event for the tigger to use. It's recusive
+        * safe and will not be recorded anywhere.
+        */
+       if (!entry && ftrace_file->flags & FTRACE_EVENT_FL_TRIGGER_COND) {
+               *current_rb = temp_buffer;
+               entry = trace_buffer_lock_reserve(*current_rb,
+                                                 type, len, flags, pc);
+       }
+       return entry;
 }
 EXPORT_SYMBOL_GPL(trace_event_buffer_lock_reserve);
 
@@ -6494,11 +6510,16 @@ __init static int tracer_alloc_buffers(void)
 
        raw_spin_lock_init(&global_trace.start_lock);
 
+       /* Used for event triggers */
+       temp_buffer = ring_buffer_alloc(PAGE_SIZE, RB_FL_OVERWRITE);
+       if (!temp_buffer)
+               goto out_free_cpumask;
+
        /* TODO: make the number of buffers hot pluggable with CPUS */
        if (allocate_trace_buffers(&global_trace, ring_buf_size) < 0) {
                printk(KERN_ERR "tracer: failed to allocate ring buffer!\n");
                WARN_ON(1);
-               goto out_free_cpumask;
+               goto out_free_temp_buffer;
        }
 
        if (global_trace.buffer_disabled)
@@ -6540,6 +6561,8 @@ __init static int tracer_alloc_buffers(void)
 
        return 0;
 
+out_free_temp_buffer:
+       ring_buffer_free(temp_buffer);
 out_free_cpumask:
        free_percpu(global_trace.trace_buffer.data);
 #ifdef CONFIG_TRACER_MAX_TRACE