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SubjectRe: [PATCH 05/11] perf: New PERF_EVENT_IOC_INJECT ioctl
On Wed, Feb 03, 2010 at 10:14:29AM +0100, Frederic Weisbecker wrote:
> The PERF_EVENT_IOC_INJECT perf event ioctl can be used to inject
> events, if the corresponding pmu and event supports it.
>
> On trace events, it will call the inject callback, usually reserved
> for events that need to catch up with the user.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
> Cc: Li Zefan <lizf@cn.fujitsu.com>
> Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
> Cc: Masami Hiramatsu <mhiramat@redhat.com>
> Cc: Jens Axboe <jens.axboe@oracle.com>
> ---
> include/linux/perf_event.h | 2 ++
> kernel/perf_event.c | 23 +++++++++++++++++++++++
> 2 files changed, 25 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 556b0f4..d2e83f0 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -228,6 +228,7 @@ struct perf_event_attr {
> #define PERF_EVENT_IOC_PERIOD _IOW('$', 4, __u64)
> #define PERF_EVENT_IOC_SET_OUTPUT _IO ('$', 5)
> #define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
> +#define PERF_EVENT_IOC_INJECT _IO ('$', 7)
>
> enum perf_event_ioc_flags {
> PERF_IOC_FLAG_GROUP = 1U << 0,
> @@ -513,6 +514,7 @@ struct pmu {
> void (*disable) (struct perf_event *event);
> void (*read) (struct perf_event *event);
> void (*unthrottle) (struct perf_event *event);
> + void (*inject) (struct perf_event *event);
> };
>
> /**
> diff --git a/kernel/perf_event.c b/kernel/perf_event.c
> index 40f8b07..e4dfd12 100644
> --- a/kernel/perf_event.c
> +++ b/kernel/perf_event.c
> @@ -2151,6 +2151,26 @@ unlock:
> return ret;
> }
>
> +static void __perf_event_inject(void *info)
> +{
> + struct perf_event *event = info;
> +
> + event->pmu->inject(event);
> +}
> +
> +static int perf_event_inject(struct perf_event *event)
> +{
> + struct perf_event_context *ctx = event->ctx;
> + struct task_struct *task = ctx->task;
> +
> + if (!event->pmu->inject || task)
> + return -EINVAL;
> +
> + smp_call_function_single(event->cpu, __perf_event_inject, event, 1);
> +



Ah, I forgot to say. Injection is only supported on cpu
bound events (non-task bound). Because if it is task-bound,
we can't ensure we can inject while the event is scheduled,
not sure how to fix this.



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