From: Jiri Olsa <jolsa@redhat.com>
To: mingo@elte.hu, rostedt@goodmis.org, andi@firstfloor.org,
lwoodman@redhat.com, hch@infradead.org
Cc: linux-kernel@vger.kernel.org, Jiri Olsa <jolsa@redhat.com>
Subject: [PATCHv2 1/2] tracing - fix recursive user stack trace
Date: Thu, 11 Nov 2010 10:09:08 +0100 [thread overview]
Message-ID: <1289466549-7602-2-git-send-email-jolsa@redhat.com> (raw)
In-Reply-To: <20101110164413.GA5360@nowhere>
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.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
---
kernel/trace/trace.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 82d9b81..1905a72 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 +1304,16 @@ 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 +1331,11 @@ 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
next prev parent reply other threads:[~2010-11-11 9:09 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-10 11:56 [PATCH 0/2] tracing,mm - add kernel pagefault tracepoint for x86 & x86_64 Jiri Olsa
2010-11-10 11:56 ` [PATCH 1/2] " Jiri Olsa
2010-11-10 13:29 ` Christoph Hellwig
2010-11-10 13:44 ` Jiri Olsa
2010-11-10 13:52 ` Ingo Molnar
2010-11-10 15:00 ` Frederic Weisbecker
2010-11-10 15:17 ` Jiri Olsa
2010-11-10 15:20 ` Christoph Hellwig
2010-11-10 16:28 ` Andi Kleen
2010-11-10 16:44 ` Frederic Weisbecker
2010-11-11 9:09 ` [PATCHv2 0/2] " Jiri Olsa
2010-11-11 9:09 ` Jiri Olsa [this message]
2010-11-11 10:34 ` [PATCHv2 1/2] tracing - fix recursive user stack trace Andi Kleen
2010-11-11 9:09 ` [PATCHv2 2/2] tracing,mm - add kernel pagefault tracepoint for x86 & x86_64 Jiri Olsa
2010-11-11 12:51 ` Christoph Hellwig
2010-11-11 13:15 ` Jiri Olsa
2010-11-15 13:43 ` Frederic Weisbecker
2010-11-15 14:06 ` Andi Kleen
2010-11-15 14:54 ` Frederic Weisbecker
2010-11-15 15:04 ` Steven Rostedt
2010-11-15 14:19 ` Steven Rostedt
2010-11-16 9:23 ` Jiri Olsa
2010-11-16 13:13 ` Steven Rostedt
2010-11-10 11:56 ` [PATCH 2/2] tracing - fix recursive user stack trace Jiri Olsa
2010-11-11 0:13 ` Li Zefan
2010-11-11 21:57 ` Steven Rostedt
2010-11-18 14:05 ` [tip:perf/core] tracing: Fix " tip-bot for Steven Rostedt
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