On Tue, 09 Apr 2013 20:46:27 -0400, Steven Rostedt wrote:
> On Wed, 2013-04-10 at 09:36 +0900, Namhyung Kim wrote:
>
>> You meant iter->cpu_file != RING_BUFFER_ALL_CPUS case, right?
>
> Yep.
>
>>
>> So why bother trying to check other cpus then?
>
> Because it's a very slow path (closing a file), and it keeps the code
> simpler and more condense.
>
> We could add your change for consistency, but right now, its very low
> priority.
Hmm.. okay.
>
> But looking at the code, I do see a clean up that looks like it would be
> worth updating. If the ring_buffer_read_prepare() fails, we should
> probably let the user know, instead of succeeding and then having no
> output.
How about below.. :)
>From 7ba245dba217ef858b467552019acd49f7fdce7e Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung....@lge.com>
Date: Wed, 10 Apr 2013 09:10:44 +0900
Subject: [PATCH] tracing: Check result of ring_buffer_read_prepare()
The ring_buffer_read_prepare() can return NULL if memory allocation
fails. Fail out in this case instead of succedding and then having
no output.
Suggested-by: Steven Rostedt <rost...@goodmis.org>
Signed-off-by: Namhyung Kim <namhy...@kernel.org>
---
kernel/trace/trace.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7270460cfe3c..3b3514dc8e5e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2826,6 +2826,8 @@ __tracing_open(struct inode *inode, struct file *file,
bool snapshot)
for_each_tracing_cpu(cpu) {
iter->buffer_iter[cpu] =
ring_buffer_read_prepare(iter->trace_buffer->buffer, cpu);
+ if (!iter->buffer_iter[cpu])
+ goto free;
}
ring_buffer_read_prepare_sync();
for_each_tracing_cpu(cpu) {
@@ -2836,6 +2838,9 @@ __tracing_open(struct inode *inode, struct file *file,
bool snapshot)
cpu = iter->cpu_file;
iter->buffer_iter[cpu] =
ring_buffer_read_prepare(iter->trace_buffer->buffer,
cpu);
+ if (!iter->buffer_iter[cpu])
+ goto free;
+
ring_buffer_read_prepare_sync();
ring_buffer_read_start(iter->buffer_iter[cpu]);
tracing_iter_reset(iter, cpu);
@@ -2847,6 +2852,26 @@ __tracing_open(struct inode *inode, struct file *file,
bool snapshot)
return iter;
+free:
+ if (iter->cpu_file == RING_BUFFER_ALL_CPUS) {
+ for_each_tracing_cpu(cpu) {
+ if (iter->buffer_iter[cpu])
+ ring_buffer_read_finish(iter->buffer_iter[cpu]);
+ }
+ } else {
+ cpu = iter->cpu_file;
+ if (iter->buffer_iter[cpu])
+ ring_buffer_read_finish(iter->buffer_iter[cpu]);
+ }
+
+ if (iter->trace && iter->trace->close)
+ iter->trace->close(iter);
+
+ if (!iter->snapshot)
+ tracing_start_tr(tr);
+
+ mutex_destroy(&iter->mutex);
+ free_cpumask_var(iter->started);
fail:
mutex_unlock(&trace_types_lock);
kfree(iter->trace);
--
1.7.11.7
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