[tip:perf/urgent] perf_events, trace: Fix probe unregister race

tip-bot for Peter Zijlstra
2010-05-31T07:20:18Z

Commit-ID: 3771f0771154675d4a0ca780be2411f3cc357208
Gitweb: http://git.kernel.org/tip/3771f0771154675d4a0ca780be2411f3cc357208
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 21 May 2010 12:31:09 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 31 May 2010 08:46:09 +0200

perf_events, trace: Fix probe unregister race

tracepoint_probe_unregister() does not synchronize against the probe
callbacks, so do that explicitly. This properly serializes the callbacks
and the free of the data used therein.

Also, use this_cpu_ptr() where possible.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1274438476.1674.1702.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/trace/ftrace.h | 2 +-
kernel/trace/trace_event_perf.c | 10 ++++++++--
kernel/trace/trace_kprobe.c | 4 ++--
kernel/trace/trace_syscalls.c | 4 ++--
4 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 3d685d1..5a64905 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -725,7 +725,7 @@ perf_trace_##call(void *__data, proto) \
\
{ assign; } \
\
- head = per_cpu_ptr(event_call->perf_events, smp_processor_id());\
+ head = this_cpu_ptr(event_call->perf_events); \
perf_trace_buf_submit(entry, __entry_size, rctx, __addr, \
__count, &__regs, head); \
}
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index cb6f365..49c7abf 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -116,7 +116,7 @@ int perf_trace_enable(struct perf_event *p_event)
if (WARN_ON_ONCE(!list))
return -EINVAL;

- list = per_cpu_ptr(list, smp_processor_id());
+ list = this_cpu_ptr(list);
hlist_add_head_rcu(&p_event->hlist_entry, list);

return 0;
@@ -142,6 +142,12 @@ void perf_trace_destroy(struct perf_event *p_event)
tp_event->class->perf_probe,
tp_event);

+ /*
+ * Ensure our callback won't be called anymore. See
+ * tracepoint_probe_unregister() and __DO_TRACE().
+ */
+ synchronize_sched();
+
free_percpu(tp_event->perf_events);
tp_event->perf_events = NULL;

@@ -169,7 +175,7 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
if (*rctxp < 0)
return NULL;

- raw_data = per_cpu_ptr(perf_trace_buf[*rctxp], smp_processor_id());
+ raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);

/* zero the dead bytes from align to not leak stack to user */
memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index faf7cef..f52b5f5 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1359,7 +1359,7 @@ static __kprobes void kprobe_perf_func(struct kprobe *kp,
for (i = 0; i < tp->nr_args; i++)
call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);

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

@@ -1392,7 +1392,7 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
for (i = 0; i < tp->nr_args; i++)
call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);

- head = per_cpu_ptr(call->perf_events, smp_processor_id());
+ head = this_cpu_ptr(call->perf_events);
perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1, regs, head);
}

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index d2c859c..34e3580 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -519,7 +519,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
syscall_get_arguments(current, regs, 0, sys_data->nb_args,
(unsigned long *)&rec->args);

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

@@ -595,7 +595,7 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
rec->nr = syscall_nr;
rec->ret = syscall_get_return_value(current, regs);

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