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Subject[PATCH 1/4] perf: allow building PMU driver as module
Date
This patch adds support for building PMU driver as module. It exports
function perf_pmu_{register,unregister} and adds reference tracking
for PMU driver module. When PMU driver is built as module, each active
event of the PMU holds a reference to the driver module.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
---
include/linux/perf_event.h | 1 +
kernel/events/core.c | 15 +++++++++++++++
2 files changed, 16 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index e56b07f..4f0710e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -172,6 +172,7 @@ struct perf_event;
struct pmu {
struct list_head entry;

+ struct module *module;
struct device *dev;
const struct attribute_group **attr_groups;
const char *name;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 661951a..1616b7d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -39,6 +39,7 @@
#include <linux/hw_breakpoint.h>
#include <linux/mm_types.h>
#include <linux/cgroup.h>
+#include <linux/module.h>

#include "internal.h"

@@ -3244,6 +3245,9 @@ static void __free_event(struct perf_event *event)
if (event->ctx)
put_ctx(event->ctx);

+ if (event->pmu)
+ module_put(event->pmu->module);
+
call_rcu(&event->rcu_head, free_event_rcu);
}
static void free_event(struct perf_event *event)
@@ -6566,6 +6570,7 @@ free_pdc:
free_percpu(pmu->pmu_disable_count);
goto unlock;
}
+EXPORT_SYMBOL_GPL(perf_pmu_register);

void perf_pmu_unregister(struct pmu *pmu)
{
@@ -6587,6 +6592,7 @@ void perf_pmu_unregister(struct pmu *pmu)
put_device(pmu->dev);
free_pmu_context(pmu);
}
+EXPORT_SYMBOL_GPL(perf_pmu_unregister);

struct pmu *perf_init_event(struct perf_event *event)
{
@@ -6600,6 +6606,10 @@ struct pmu *perf_init_event(struct perf_event *event)
pmu = idr_find(&pmu_idr, event->attr.type);
rcu_read_unlock();
if (pmu) {
+ if (!try_module_get(pmu->module)) {
+ pmu = ERR_PTR(-ENODEV);
+ goto unlock;
+ }
event->pmu = pmu;
ret = pmu->event_init(event);
if (ret)
@@ -6608,6 +6618,10 @@ struct pmu *perf_init_event(struct perf_event *event)
}

list_for_each_entry_rcu(pmu, &pmus, entry) {
+ if (!try_module_get(pmu->module)) {
+ pmu = ERR_PTR(-ENODEV);
+ goto unlock;
+ }
event->pmu = pmu;
ret = pmu->event_init(event);
if (!ret)
@@ -6786,6 +6800,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
err_pmu:
if (event->destroy)
event->destroy(event);
+ module_put(pmu->module);
err_ns:
if (event->ns)
put_pid_ns(event->ns);
--
1.8.5.3


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