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authorLinus Torvalds <torvalds@linux-foundation.org>2014-03-26 09:09:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-03-26 09:09:18 -0700
commitf217c44ebd41ce7369d2df07622b2839479183b0 (patch)
treec8ee34e6d2b20e068c5241fbe663983ab0a1a88d /kernel
parentfce7fc79c8f7188dfc5eafa1b937bcc3c5a4c2f5 (diff)
parent2c4a33aba5f9ea3a28f2e40351f078d95f00786b (diff)
Merge tag 'trace-fixes-v3.14-rc7-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fix from Steven Rostedt: "While on my flight to Linux Collaboration Summit, I was working on my slides for the event trigger tutorial. I booted a 3.14-rc7 kernel to perform what I wanted to teach and cut and paste it into my slides. When I tried the traceon event trigger with a condition attached to it (turns tracing on only if a field of the trigger event matches a condition set by the user), nothing happened. Tracing would not turn on. I stopped working on my presentation in order to find what was wrong. It ended up being the way trace event triggers work when they have conditions. Instead of copying the fields, the condition code just looks at the fields that were copied into the ring buffer. This works great, unless tracing is off. That's because when the event is reserved on the ring buffer, the ring buffer returns a NULL pointer, this tells the tracing code that the ring buffer is disabled. This ends up being a problem for the traceon trigger if it is using this information to check its condition. Luckily the code that checks if tracing is on returns the ring buffer to use (because the ring buffer is determined by the event file also passed to that field). I was able to easily solve this bug by checking in that helper function if the returned ring buffer entry is NULL, and if so, also check the file flag if it has a trace event trigger condition, and if so, to pass back a temp ring buffer to use. This will allow the trace event trigger condition to still test the event fields, but nothing will be recorded" * tag 'trace-fixes-v3.14-rc7-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Fix traceon trigger condition to actually turn tracing on
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c27
1 files changed, 25 insertions, 2 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 815c878f409b..24c1f2382557 100644
--- 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