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authorOleg Nesterov <oleg@redhat.com>2013-06-20 19:38:06 +0200
committerSteven Rostedt <rostedt@goodmis.org>2013-07-01 20:34:23 -0400
commit288e984e622336bab8bc3dfdf2f190816362d9a1 (patch)
treef760ff7bfe1278767f1dd2e2a95d91768ab5ecee
parent6e94a780374ed31b280f939d4757e8d7858dff16 (diff)
tracing/kprobes: Avoid perf_trace_buf_*() if ->perf_events is empty
perf_trace_buf_prepare() + perf_trace_buf_submit() make no sense if this task/CPU has no active counters. Change kprobe_perf_func() and kretprobe_perf_func() to check call->perf_events beforehand and return if this list is empty. For example, "perf record -e some_probe -p1". Only /sbin/init will report, all other threads which hit the same probe will do perf_trace_buf_prepare/perf_trace_buf_submit just to realize that nobody wants perf_swevent_event(). Link: http://lkml.kernel.org/r/20130620173806.GA13151@redhat.com Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--kernel/trace/trace_kprobe.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index f2374172ba7b..c35bebe53ffe 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1156,6 +1156,10 @@ kprobe_perf_func(struct trace_probe *tp, struct pt_regs *regs)
int size, __size, dsize;
int rctx;
+ head = this_cpu_ptr(call->perf_events);
+ if (hlist_empty(head))
+ return;
+
dsize = __get_data_size(tp, regs);
__size = sizeof(*entry) + tp->size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
@@ -1171,8 +1175,6 @@ kprobe_perf_func(struct trace_probe *tp, struct pt_regs *regs)
entry->ip = (unsigned long)tp->rp.kp.addr;
memset(&entry[1], 0, dsize);
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, NULL);
}
@@ -1188,6 +1190,10 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri,
int size, __size, dsize;
int rctx;
+ head = this_cpu_ptr(call->perf_events);
+ if (hlist_empty(head))
+ return;
+
dsize = __get_data_size(tp, regs);
__size = sizeof(*entry) + tp->size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
@@ -1203,8 +1209,6 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri,
entry->func = (unsigned long)tp->rp.kp.addr;
entry->ret_ip = (unsigned long)ri->ret_addr;
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, NULL);
}