[PATCH] trace: add ability to set a target task for events

From: Andrew Vagin
Date: Wed Jul 04 2012 - 05:08:47 EST


From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>

A few events are interesting not only for a current task.
For example, sched_stat_* are interesting to a task, which
wake up. For this reason, it will be good, if such events will
be delivered to a target task too.

Now a target task can be set by using __perf_task().

The original idea and a draft patch belongs to Peter Zijlstra.

Inspired-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Arun Sharma <asharma@xxxxxx>
Signed-off-by: Andrew Vagin <avagin@xxxxxxxxxx>
---
include/linux/ftrace_event.h | 5 +++--
include/linux/perf_event.h | 3 ++-
include/trace/events/sched.h | 1 +
include/trace/ftrace.h | 6 +++++-
kernel/events/core.c | 26 +++++++++++++++++++++++++-
kernel/trace/trace_event_perf.c | 2 +-
kernel/trace/trace_kprobe.c | 4 ++--
kernel/trace/trace_syscalls.c | 4 ++--
8 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 176a939..55b96e3 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -303,9 +303,10 @@ extern void *perf_trace_buf_prepare(int size, unsigned short type,

static inline void
perf_trace_buf_submit(void *raw_data, int size, int rctx, u64 addr,
- u64 count, struct pt_regs *regs, void *head)
+ u64 count, struct pt_regs *regs, void *head,
+ struct task_struct *task)
{
- perf_tp_event(addr, count, raw_data, size, regs, head, rctx);
+ perf_tp_event(addr, count, raw_data, size, regs, head, rctx, task);
}
#endif

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 45db49f..14acc5d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1269,7 +1269,8 @@ static inline bool perf_paranoid_kernel(void)
extern void perf_event_init(void);
extern void perf_tp_event(u64 addr, u64 count, void *record,
int entry_size, struct pt_regs *regs,
- struct hlist_head *head, int rctx);
+ struct hlist_head *head, int rctx,
+ struct task_struct *task);
extern void perf_bp_event(struct perf_event *event, void *data);

#ifndef perf_misc_flags
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index ea7a203..9e3999a 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -325,6 +325,7 @@ DECLARE_EVENT_CLASS(sched_stat_template,
)
TP_perf_assign(
__perf_count(delay);
+ __perf_task(tsk);
),

TP_printk("comm=%s pid=%d delay=%Lu [ns]",
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 7697249..db14daf 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -711,6 +711,9 @@ __attribute__((section("_ftrace_events"))) *__event_##call = &event_##call
#undef __perf_count
#define __perf_count(c) __count = (c)

+#undef __perf_task
+#define __perf_task(t) __task = (t)
+
#undef TP_perf_assign
#define TP_perf_assign(args...) args

@@ -724,6 +727,7 @@ perf_trace_##call(void *__data, proto) \
struct ftrace_raw_##call *entry; \
struct pt_regs __regs; \
u64 __addr = 0, __count = 1; \
+ struct task_struct *__task = NULL; \
struct hlist_head *head; \
int __entry_size; \
int __data_size; \
@@ -751,7 +755,7 @@ perf_trace_##call(void *__data, proto) \
\
head = this_cpu_ptr(event_call->perf_events); \
perf_trace_buf_submit(entry, __entry_size, rctx, __addr, \
- __count, &__regs, head); \
+ __count, &__regs, head, __task); \
}

/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d7d71d6..164c309 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5207,7 +5207,8 @@ static int perf_tp_event_match(struct perf_event *event,
}

void perf_tp_event(u64 addr, u64 count, void *record, int entry_size,
- struct pt_regs *regs, struct hlist_head *head, int rctx)
+ struct pt_regs *regs, struct hlist_head *head, int rctx,
+ struct task_struct *task)
{
struct perf_sample_data data;
struct perf_event *event;
@@ -5226,6 +5227,29 @@ void perf_tp_event(u64 addr, u64 count, void *record, int entry_size,
perf_swevent_event(event, count, &data, regs);
}

+ /*
+ * If we got specified a target task, also iterate its context and
+ * deliver this event there too.
+ */
+ if (task && task != current) {
+ struct perf_event_context *ctx;
+ struct trace_entry *entry = record;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(task->perf_event_ctxp[perf_sw_context]);
+ if (!ctx)
+ goto unlock;
+
+ list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+ if (entry->type != event->attr.config)
+ continue;
+ if (perf_tp_event_match(event, &data, regs))
+ perf_swevent_event(event, count, &data, regs);
+ }
+unlock:
+ rcu_read_unlock();
+ }
+
perf_swevent_put_recursion_context(rctx);
}
EXPORT_SYMBOL_GPL(perf_tp_event);
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index fee3752..8a6d2ee 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -281,7 +281,7 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip)

head = this_cpu_ptr(event_function.perf_events);
perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
- 1, &regs, head);
+ 1, &regs, head, NULL);

#undef ENTRY_SIZE
}
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index b31d3d5..2feeaa0 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1002,7 +1002,7 @@ static __kprobes void kprobe_perf_func(struct kprobe *kp,
store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);

head = this_cpu_ptr(call->perf_events);
- perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head);
+ perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head, NULL);
}

/* Kretprobe profile handler */
@@ -1033,7 +1033,7 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);

head = this_cpu_ptr(call->perf_events);
- perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1, regs, head);
+ perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1, regs, head, NULL);
}
#endif /* CONFIG_PERF_EVENTS */

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 96fc733..60e4d78 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -532,7 +532,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
(unsigned long *)&rec->args);

head = this_cpu_ptr(sys_data->enter_event->perf_events);
- perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head);
+ perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}

int perf_sysenter_enable(struct ftrace_event_call *call)
@@ -608,7 +608,7 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
rec->ret = syscall_get_return_value(current, regs);

head = this_cpu_ptr(sys_data->exit_event->perf_events);
- perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head);
+ perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}

int perf_sysexit_enable(struct ftrace_event_call *call)
--
1.7.1

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