Usually, pmus that do, for example, instruction tracing, would only ever be able to have one event per task per cpu (or per perf_context). For such pmus it makes sense to disallow creating conflicting events early on, so as to provide consistent behavior for the user.
This patch adds a pmu capability that indicates such constraint on event creation. Signed-off-by: Alexander Shishkin <[email protected]> --- include/linux/perf_event.h | 1 + kernel/events/core.c | 38 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 3d68411..b6f7408 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -277,6 +277,7 @@ struct pmu { #define PERF_PMU_CAP_NO_INTERRUPT 1 #define PERF_PMU_CAP_AUX_NO_SG 2 #define PERF_PMU_CAP_AUX_SW_DOUBLEBUF 4 +#define PERF_PMU_CAP_EXCLUSIVE 8 /** * enum perf_event_active_state - the states of a event diff --git a/kernel/events/core.c b/kernel/events/core.c index 48ad31b..9783c60 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7113,6 +7113,32 @@ out: return ret; } +static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2) +{ + if ((e1->pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE) && + (e1->cpu == e2->cpu || + e1->cpu == -1 || + e2->cpu == -1)) + return true; + return false; +} + +static bool exclusive_event_ok(struct perf_event *event, + struct perf_event_context *ctx) +{ + struct perf_event *iter_event; + + if (!(event->pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE)) + return true; + + list_for_each_entry(iter_event, &ctx->event_list, event_entry) { + if (exclusive_event_match(iter_event, event)) + return false; + } + + return true; +} + /** * sys_perf_event_open - open a performance event, associate it to a task/cpu * @@ -7261,6 +7287,11 @@ SYSCALL_DEFINE5(perf_event_open, goto err_alloc; } + if (!exclusive_event_ok(event, ctx)) { + err = -EBUSY; + goto err_context; + } + if (task) { put_task_struct(task); task = NULL; @@ -7427,6 +7458,13 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, goto err_free; } + if (!exclusive_event_ok(event, ctx)) { + perf_unpin_context(ctx); + put_ctx(ctx); + err = -EBUSY; + goto err_free; + } + WARN_ON_ONCE(ctx->parent_ctx); mutex_lock(&ctx->mutex); perf_install_in_context(ctx, event, cpu); -- 2.0.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
