From 288e984e622336bab8bc3dfdf2f190816362d9a1 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 20 Jun 2013 19:38:06 +0200 Subject: [PATCH] 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 Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/trace/trace_kprobe.c | 12 ++++++++---- 1 file 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); } -- 2.20.1