On Fri, Jan 22, 2016 at 12:13:49PM +0000, Wang Nan wrote:
> Add new ioctl() to pause/resume ring-buffer output.
>
> In some situations we want to read from ring buffer only when we
> ensure nothing can write to the ring buffer during reading. Without
> this patch we have to turn off all events attached to this ring buffer.
> This patch is for supporting overwritable ring buffer with TAILSIZE
> selected.
TAILSIZE is dropped. pls adjust commit log.
> Signed-off-by: Wang Nan <wangn...@huawei.com>
> Cc: He Kuang <heku...@huawei.com>
> Cc: Alexei Starovoitov <a...@kernel.org>
> Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
> Cc: Brendan Gregg <brendan.d.gr...@gmail.com>
> Cc: Jiri Olsa <jo...@kernel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
> Cc: Namhyung Kim <namhy...@kernel.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Zefan Li <lize...@huawei.com>
> Cc: pi3or...@163.com
> ---
> include/uapi/linux/perf_event.h | 1 +
> kernel/events/core.c | 13 +++++++++++++
> kernel/events/internal.h | 11 +++++++++++
> kernel/events/ring_buffer.c | 7 ++++++-
> 4 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 1afe962..2c7f00c 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -401,6 +401,7 @@ struct perf_event_attr {
> #define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
> #define PERF_EVENT_IOC_ID _IOR('$', 7, __u64 *)
> #define PERF_EVENT_IOC_SET_BPF _IOW('$', 8, __u32)
> +#define PERF_EVENT_IOC_PAUSE_OUTPUT _IO ('$', 9)
do you need to add '__u32' here, since boolean flag is passed to it?
> + case PERF_EVENT_IOC_PAUSE_OUTPUT: {
> + struct ring_buffer *rb;
> +
> + rcu_read_lock();
> + rb = rcu_dereference(event->rb);
> + if (!event->rb) {
> + rcu_read_unlock();
> + return -EINVAL;
> + }
> + rb_toggle_paused(rb, !!arg);
> + rcu_read_unlock();
> + return 0;
> + }
