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Date: Mon, 26 Sep 2011 19:55:34 +0400
From: Andrew Vagin <avagin@...nvz.org>
To: linux-kernel@...r.kernel.org
Cc: Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
avagin@...nvz.org
Subject: [PATCH 3/4] trace: add ability to collect call chain of non-current task.
An event may requires call chain of non-current task. E.g. You may want
to know where and how long a task is sleeping. A time slice is known
when the task wakes up. We can send event in this moment, but a target
task isn't "current".
The macro __perf_task set a task for which a call chain will be
collected.
Know issues:
* Now call chains for non-current tasks are collected on x86 only,
but it may be done for other architectures simply.
* It collects only kernel call chains, because we can't get direct
access to memory of other processes and this operation should be
fast enough.
Signed-off-by: Andrew Vagin <avagin@...nvz.org>
---
arch/x86/kernel/cpu/perf_event.c | 8 +++-----
include/trace/ftrace.h | 11 +++++++++--
kernel/events/core.c | 30 ++++++++++++++++++------------
3 files changed, 30 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index c3d229d..18817a8 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1839,17 +1839,15 @@ void
perf_callchain_kernel(struct perf_callchain_entry *entry,
struct task_struct *tsk, struct pt_regs *regs)
{
- if (!regs)
- return;
-
if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
/* TODO: We don't support guest os callchain now */
return;
}
- perf_callchain_store(entry, regs->ip);
+ if (regs)
+ perf_callchain_store(entry, regs->ip);
- dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
+ dump_trace(tsk, regs, NULL, 0, &backtrace_ops, entry);
}
#ifdef CONFIG_COMPAT
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 5e4c72a..d03e926 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
@@ -722,7 +725,8 @@ perf_trace_##call(void *__data, proto) \
struct ftrace_event_call *event_call = __data; \
struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
struct ftrace_raw_##call *entry; \
- struct pt_regs __regs; \
+ struct pt_regs __regs, *__pregs = &__regs; \
+ struct task_struct *__task = current; \
u64 __addr = 0, __count = 1; \
struct hlist_head *head; \
int __entry_size; \
@@ -749,9 +753,12 @@ perf_trace_##call(void *__data, proto) \
\
{ assign; } \
\
+ if (__task != current) \
+ __pregs = NULL; \
+ \
head = this_cpu_ptr(event_call->perf_events); \
perf_tp_event(__addr, __count, entry, __entry_size, \
- current, &__regs, head, rctx); \
+ __task, __pregs, head, rctx); \
}
/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 41ce4db..2dce0f9 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2757,16 +2757,16 @@ static struct perf_callchain_entry
entry->nr = 0;
- if (!user_mode(regs)) {
+ if (!regs || !user_mode(regs)) {
perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
perf_callchain_kernel(entry, tsk, regs);
- if (current->mm)
- regs = task_pt_regs(current);
+ if (tsk->mm)
+ regs = task_pt_regs(tsk);
else
regs = NULL;
}
- if (regs) {
+ if (tsk == current && regs) {
perf_callchain_store(entry, PERF_CONTEXT_USER);
perf_callchain_user(entry, regs);
}
@@ -3746,7 +3746,8 @@ EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
static void __perf_event_header__init_id(struct perf_event_header *header,
struct perf_sample_data *data,
- struct perf_event *event)
+ struct perf_event *event,
+ struct task_struct *tsk)
{
u64 sample_type = event->attr.sample_type;
@@ -3755,8 +3756,8 @@ static void __perf_event_header__init_id(struct perf_event_header *header,
if (sample_type & PERF_SAMPLE_TID) {
/* namespace issues */
- data->tid_entry.pid = perf_event_pid(event, current);
- data->tid_entry.tid = perf_event_tid(event, current);
+ data->tid_entry.pid = perf_event_pid(event, tsk);
+ data->tid_entry.tid = perf_event_tid(event, tsk);
}
if (sample_type & PERF_SAMPLE_TIME)
@@ -3779,7 +3780,7 @@ void perf_event_header__init_id(struct perf_event_header *header,
struct perf_event *event)
{
if (event->attr.sample_id_all)
- __perf_event_header__init_id(header, data, event);
+ __perf_event_header__init_id(header, data, event, current);
}
static void __perf_event__output_id_sample(struct perf_output_handle *handle,
@@ -4000,12 +4001,17 @@ void perf_prepare_sample(struct perf_event_header *header,
header->size = sizeof(*header) + event->header_size;
header->misc = 0;
- header->misc |= perf_misc_flags(regs);
- __perf_event_header__init_id(header, data, event);
+ __perf_event_header__init_id(header, data, event, tsk);
- if (sample_type & PERF_SAMPLE_IP)
- data->ip = perf_instruction_pointer(regs);
+ if (regs) {
+ header->misc |= perf_misc_flags(regs);
+ if (sample_type & PERF_SAMPLE_IP)
+ data->ip = perf_instruction_pointer(regs);
+ } else {
+ header->misc |= PERF_RECORD_MISC_KERNEL;
+ data->ip = 0;
+ }
if (sample_type & PERF_SAMPLE_CALLCHAIN) {
int size = 1;
--
1.7.1
--
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