Messages in this thread Patch in this message | | | From | Alexander Shishkin <> | Subject | [PATCH v4 05/22] perf: Add a pmu capability for "exclusive" events | Date | Wed, 20 Aug 2014 15:36:02 +0300 |
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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 <alexander.shishkin@linux.intel.com> --- include/linux/perf_event.h | 1 + kernel/events/core.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 46 insertions(+)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 1e7b659b49..6bd3e743b1 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -173,6 +173,7 @@ struct perf_event; #define PERF_PMU_CAP_NO_INTERRUPT 0x01 #define PERF_PMU_CAP_AUX_NO_SG 0x02 #define PERF_PMU_CAP_AUX_SW_DOUBLEBUF 0x04 +#define PERF_PMU_CAP_EXCLUSIVE 0x08 /** * struct pmu - generic performance monitoring unit diff --git a/kernel/events/core.c b/kernel/events/core.c index 63d98d6998..67f857ab56 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7248,6 +7248,32 @@ 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 * @@ -7399,6 +7425,11 @@ SYSCALL_DEFINE5(perf_event_open, goto err_alloc; } + if ((pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE) && group_leader) { + err = -EBUSY; + goto err_context; + } + if (task) { put_task_struct(task); task = NULL; @@ -7484,6 +7515,12 @@ SYSCALL_DEFINE5(perf_event_open, } } + if (!exclusive_event_ok(event, ctx)) { + mutex_unlock(&ctx->mutex); + fput(event_file); + goto err_context; + } + perf_install_in_context(ctx, event, event->cpu); perf_unpin_context(ctx); mutex_unlock(&ctx->mutex); @@ -7570,6 +7607,14 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, WARN_ON_ONCE(ctx->parent_ctx); mutex_lock(&ctx->mutex); + if (!exclusive_event_ok(event, ctx)) { + mutex_unlock(&ctx->mutex); + perf_unpin_context(ctx); + put_ctx(ctx); + err = -EBUSY; + goto err_free; + } + perf_install_in_context(ctx, event, cpu); perf_unpin_context(ctx); mutex_unlock(&ctx->mutex); -- 2.1.0
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