Messages in this thread Patch in this message | | | Date | Fri, 14 Nov 2014 13:21:56 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH 02/23 v4] tracing: Add trace_seq_has_overflowed() and trace_handle_return() |
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On Fri, 14 Nov 2014 12:25:23 +0100 Petr Mladek <pmladek@suse.cz> wrote:
> > @@ -193,7 +184,6 @@ int ftrace_raw_output_prep(struct trace_iterator *iter, > > struct trace_seq *s = &iter->seq; > > struct trace_seq *p = &iter->tmp_seq; > > struct trace_entry *entry; > > - int ret; > > > > event = container_of(trace_event, struct ftrace_event_call, event); > > entry = iter->ent; > > @@ -204,8 +194,9 @@ int ftrace_raw_output_prep(struct trace_iterator *iter, > > } > > > > trace_seq_init(p); > > - ret = trace_seq_printf(s, "%s: ", ftrace_event_name(event)); > > - if (!ret) > > + trace_seq_printf(s, "%s: ", ftrace_event_name(event)); > > + > > + if (trace_seq_has_overflowed(s)) > > return TRACE_TYPE_PARTIAL_LINE; > > > > return 0; > > This looks like a bug in the original code. It returns 0 in each case > because TRACE_TYPE_PARTIAL_LINE == 0. I guess that the last three > lines should get replaced by > > return trace_handle_return(s); > > as it is done in the other functions.
Here's the fix for this:
-- Steve
From 5986fa1aee34cbfe2513d7a20d2590fb2a1fc1f2 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> Date: Fri, 14 Nov 2014 11:42:06 -0500 Subject: [PATCH] tracing: Fix return value of ftrace_raw_output_prep()
If the trace_seq of ftrace_raw_output_prep() is full this function returns TRACE_TYPE_PARTIAL_LINE, otherwise it returns zero.
The problem is that TRACE_TYPE_PARTIAL_LINE happens to be zero!
The thing is, the caller of ftrace_raw_output_prep() expects a success to be zero. Change that to expect it to be TRACE_TYPE_HANDLED.
Link: http://lkml.kernel.org/r/20141114112522.GA2988@dhcp128.suse.cz
Reminded-by: Petr Mladek <pmladek@suse.cz> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- include/trace/ftrace.h | 2 +- kernel/trace/trace_output.c | 5 +---- 2 files changed, 2 insertions(+), 5 deletions(-)
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h index f13471b5d27a..139b5067345b 100644 --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -277,7 +277,7 @@ ftrace_raw_output_##call(struct trace_iterator *iter, int flags, \ field = (typeof(field))iter->ent; \ \ ret = ftrace_raw_output_prep(iter, trace_event); \ - if (ret) \ + if (ret != TRACE_TYPE_HANDLED) \ return ret; \ \ trace_seq_printf(s, print); \ diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 163c11b6b8ff..723818bc83b4 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -196,10 +196,7 @@ int ftrace_raw_output_prep(struct trace_iterator *iter, trace_seq_init(p); trace_seq_printf(s, "%s: ", ftrace_event_name(event)); - if (trace_seq_has_overflowed(s)) - return TRACE_TYPE_PARTIAL_LINE; - - return 0; + return trace_handle_return(s); } EXPORT_SYMBOL(ftrace_raw_output_prep); -- 1.8.1.4
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