From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932502Ab0KLPMp (ORCPT ); Fri, 12 Nov 2010 10:12:45 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:40795 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932442Ab0KLPMY (ORCPT ); Fri, 12 Nov 2010 10:12:24 -0500 X-Authority-Analysis: v=1.1 cv=6ptpMFIBtxRk0xdOb6IhJTbTLVRlKjWFes7R4SsWCrA= c=1 sm=0 a=hHUGQOVUbM8A:10 a=bbbx4UPp9XUA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=20KFwNOVAAAA:8 a=meVymXHHAAAA:8 a=AgZKqvVX_7YeQFwo2cUA:9 a=HHv1o2s-yiuT5b8Wmt8A:7 a=q7QeflhYWY_7-ic_ictTKi94KbMA:4 a=DHQQ7jDAcw4A:10 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Message-Id: <20101112151223.183540991@goodmis.org> User-Agent: quilt/0.48-1 Date: Fri, 12 Nov 2010 10:10:48 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Frederic Weisbecker , Jiri Olsa Subject: [PATCH 3/3] tracing: Fix recursive user stack trace References: <20101112151045.672405637@goodmis.org> Content-Disposition: inline; filename=0003-tracing-Fix-recursive-user-stack-trace.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Steven Rostedt The user stack trace can fault when examining the trace. Which would call the do_page_fault handler, which would trace again, which would do the user stack trace, which would fault and call do_page_fault again ... Thus this is causing a recursive bug. We need to have a recursion detector here. [ Resubmitted by Jiri Olsa ] Signed-off-by: Jiri Olsa LKML-Reference: <1289390172-9730-3-git-send-email-jolsa@redhat.com> Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 82d9b81..0215e87 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1284,6 +1284,8 @@ void trace_dump_stack(void) __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count()); } +static DEFINE_PER_CPU(int, user_stack_count); + void ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) { @@ -1302,6 +1304,18 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) if (unlikely(in_nmi())) return; + /* + * prevent recursion, since the user stack tracing may + * trigger other kernel events. + */ + preempt_disable(); + if (__get_cpu_var(user_stack_count)) + goto out; + + __get_cpu_var(user_stack_count)++; + + + event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK, sizeof(*entry), flags, pc); if (!event) @@ -1319,6 +1333,11 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) save_stack_trace_user(&trace); if (!filter_check_discard(call, entry, buffer, event)) ring_buffer_unlock_commit(buffer, event); + + __get_cpu_var(user_stack_count)--; + + out: + preempt_enable(); } #ifdef UNUSED -- 1.7.1