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perf: add the necessary core perf APIs when accessing events counters in eBPF programs 

This patch add three core perf APIs:
 - perf_event_attrs(): export the struct perf_event_attr from struct
   perf_event;
 - perf_event_get(): get the struct perf_event from the given fd;
 - perf_event_read_local(): read the events counters active on the
   current CPU;
These APIs are needed when accessing events counters in eBPF programs.

The API perf_event_read_local() comes from Peter and I add the
corresponding SOB.

Signed-off-by: Kaixu Xia <xiakaixu@huawei.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Kaixu Xia 2015-08-06 07:02:32 +00:00 committed by David S. Miller
parent f1d5ca4344
commit ffe8690c85
2 changed files with 88 additions and 0 deletions
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10
include/linux/perf_event.h
View File

@ -641,6 +641,8 @@ extern int perf_event_init_task(struct task_struct *child);
extern void perf_event_exit_task(struct task_struct *child);
extern void perf_event_free_task(struct task_struct *task);
extern void perf_event_delayed_put(struct task_struct *task);
extern struct perf_event *perf_event_get(unsigned int fd);
extern const struct perf_event_attr *perf_event_attrs(struct perf_event *event);
extern void perf_event_print_debug(void);
extern void perf_pmu_disable(struct pmu *pmu);
extern void perf_pmu_enable(struct pmu *pmu);
@ -659,6 +661,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr,
void *context);
extern void perf_pmu_migrate_context(struct pmu *pmu,
int src_cpu, int dst_cpu);
extern u64 perf_event_read_local(struct perf_event *event);
extern u64 perf_event_read_value(struct perf_event *event,
u64 *enabled, u64 *running);
@ -979,6 +982,12 @@ static inline int perf_event_init_task(struct task_struct *child) { return 0; }
static inline void perf_event_exit_task(struct task_struct *child) { }
static inline void perf_event_free_task(struct task_struct *task) { }
static inline void perf_event_delayed_put(struct task_struct *task) { }
static inline struct perf_event *perf_event_get(unsigned int fd) { return ERR_PTR(-EINVAL); }
static inline const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
{
return ERR_PTR(-EINVAL);
}
static inline u64 perf_event_read_local(struct perf_event *event) { return -EINVAL; }
static inline void perf_event_print_debug(void) { }
static inline int perf_event_task_disable(void) { return -EINVAL; }
static inline int perf_event_task_enable(void) { return -EINVAL; }
@ -1011,6 +1020,7 @@ static inline void perf_event_enable(struct perf_event *event) { }
static inline void perf_event_disable(struct perf_event *event) { }
static inline int __perf_event_disable(void *info) { return -1; }
static inline void perf_event_task_tick(void) { }
static inline int perf_event_release_kernel(struct perf_event *event) { return 0; }
#endif
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_NO_HZ_FULL)

78
kernel/events/core.c
View File

@ -3212,6 +3212,59 @@ static inline u64 perf_event_count(struct perf_event *event)
return __perf_event_count(event);
}
/*
* NMI-safe method to read a local event, that is an event that
* is:
* - either for the current task, or for this CPU
* - does not have inherit set, for inherited task events
* will not be local and we cannot read them atomically
* - must not have a pmu::count method
*/
u64 perf_event_read_local(struct perf_event *event)
{
unsigned long flags;
u64 val;
/*
* Disabling interrupts avoids all counter scheduling (context
* switches, timer based rotation and IPIs).
*/
local_irq_save(flags);
/* If this is a per-task event, it must be for current */
WARN_ON_ONCE((event->attach_state & PERF_ATTACH_TASK) &&
event->hw.target != current);
/* If this is a per-CPU event, it must be for this CPU */
WARN_ON_ONCE(!(event->attach_state & PERF_ATTACH_TASK) &&
event->cpu != smp_processor_id());
/*
* It must not be an event with inherit set, we cannot read
* all child counters from atomic context.
*/
WARN_ON_ONCE(event->attr.inherit);
/*
* It must not have a pmu::count method, those are not
* NMI safe.
*/
WARN_ON_ONCE(event->pmu->count);
/*
* If the event is currently on this CPU, its either a per-task event,
* or local to this CPU. Furthermore it means its ACTIVE (otherwise
* oncpu == -1).
*/
if (event->oncpu == smp_processor_id())
event->pmu->read(event);
val = local64_read(&event->count);
local_irq_restore(flags);
return val;
}
static u64 perf_event_read(struct perf_event *event)
{
/*
@ -8574,6 +8627,31 @@ void perf_event_delayed_put(struct task_struct *task)
WARN_ON_ONCE(task->perf_event_ctxp[ctxn]);
}
struct perf_event *perf_event_get(unsigned int fd)
{
int err;
struct fd f;
struct perf_event *event;
err = perf_fget_light(fd, &f);
if (err)
return ERR_PTR(err);
event = f.file->private_data;
atomic_long_inc(&event->refcount);
fdput(f);
return event;
}
const struct perf_event_attr *perf_event_attrs(struct perf_event *event)
{
if (!event)
return ERR_PTR(-EINVAL);
return &event->attr;
}
/*
* inherit a event from parent task to child task:
*/