On Wed, 2013-04-10 at 10:55 +0900, Namhyung Kim wrote:
> From: Namhyung Kim <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Namhyung Kim <[email protected]>
> ---
> kernel/trace/trace.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 7270460cfe3c..13200de31f0b 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;
> }
OK, this totally fails. I guess we need to allow
ring_buffer_read_prepare() to return NULL, as it will return NULL if a
cpu is offline or the tracing_cpumask has a CPU down.
I'll just pull this patch out of my queue for now.
-- Steve
> 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 +2852,23 @@ __tracing_open(struct inode *inode, struct file *file,
> bool snapshot)
>
> return iter;
>
> +free:
> + /*
> + * For simplicity, just keep single loop without comparing cpu_file.
> + */
> + for_each_tracing_cpu(cpu) {
> + 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);
--
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