From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759820AbZCWVRV (ORCPT ); Mon, 23 Mar 2009 17:17:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751660AbZCWVRK (ORCPT ); Mon, 23 Mar 2009 17:17:10 -0400 Received: from mail-bw0-f169.google.com ([209.85.218.169]:45297 "EHLO mail-bw0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751082AbZCWVRJ (ORCPT ); Mon, 23 Mar 2009 17:17:09 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer; b=VtXBQ0RXQDWepVIKG2VhcCgi6zJ1beARWiOUrNK/Wd1TZ4Ub/WJjgLABrpvyK/LFST /xs0dHFXVBcNgmboSWOpiqBNkYe7iLrmCG2t0mhvGljgwOOFVzwPcwfJ2R+3XVuCTcjF 3GrPbCR4jsI2kj8crs0EwzLbl13k45MOK1xT8= From: Frederic Weisbecker To: Ingo Molnar Cc: Steven Rostedt , LKML , Frederic Weisbecker Subject: [PATCH] tracing/function-graph-tracer: fix functions call traces imbalance Date: Mon, 23 Mar 2009 22:17:01 +0100 Message-Id: <1237843021-11695-1-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.6.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Impact: fix traces output Sometimes one can observe an imbalance in the traces between function calls and function return traces: func1() { } } The curly brace inside func1() is the return of another function nested inside func1. The return trace have been inserted in the buffer but not the entry. We are storing a return address on the function traces stack while we haven't inserted its entry on the buffer, hence the imbalance on the traces. This is because the tracers doesn't check all failures that can happen on buffer insertion. This patch reports the tracing recursion failures and the ring buffer failures. In such cases, we now restore the original return address for the function, giving up its return trace. Signed-off-by: Frederic Weisbecker --- kernel/trace/trace.c | 16 +++++++++++----- 1 files changed, 11 insertions(+), 5 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5c8571b..dcfb116 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -924,7 +924,7 @@ trace_function(struct trace_array *tr, } #ifdef CONFIG_FUNCTION_GRAPH_TRACER -static void __trace_graph_entry(struct trace_array *tr, +static int __trace_graph_entry(struct trace_array *tr, struct ftrace_graph_ent *trace, unsigned long flags, int pc) @@ -933,15 +933,17 @@ static void __trace_graph_entry(struct trace_array *tr, struct ftrace_graph_ent_entry *entry; if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled)))) - return; + return 0; event = trace_buffer_lock_reserve(&global_trace, TRACE_GRAPH_ENT, sizeof(*entry), flags, pc); if (!event) - return; + return 0; entry = ring_buffer_event_data(event); entry->graph_ent = *trace; ring_buffer_unlock_commit(global_trace.buffer, event); + + return 1; } static void __trace_graph_return(struct trace_array *tr, @@ -1162,6 +1164,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace) struct trace_array_cpu *data; unsigned long flags; long disabled; + int ret; int cpu; int pc; @@ -1177,15 +1180,18 @@ int trace_graph_entry(struct ftrace_graph_ent *trace) disabled = atomic_inc_return(&data->disabled); if (likely(disabled == 1)) { pc = preempt_count(); - __trace_graph_entry(tr, trace, flags, pc); + ret = __trace_graph_entry(tr, trace, flags, pc); + } else { + ret = 0; } /* Only do the atomic if it is not already set */ if (!test_tsk_trace_graph(current)) set_tsk_trace_graph(current); + atomic_dec(&data->disabled); local_irq_restore(flags); - return 1; + return ret; } void trace_graph_return(struct ftrace_graph_ret *trace) -- 1.6.1