This is a note to let you know that I've just added the patch titled
ftrace: Fix ftrace enable ordering of sysctl ftrace_enabled
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ftrace-fix-ftrace-enable-ordering-of-sysctl-ftrace_enabled.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 524a38682573b2e15ab6317ccfe50280441514be Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Fri, 6 Mar 2015 19:55:13 -0500
Subject: ftrace: Fix ftrace enable ordering of sysctl ftrace_enabled
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
commit 524a38682573b2e15ab6317ccfe50280441514be upstream.
Some archs (specifically PowerPC), are sensitive with the ordering of
the enabling of the calls to function tracing and setting of the
function to use to be traced.
That is, update_ftrace_function() sets what function the ftrace_caller
trampoline should call. Some archs require this to be set before
calling ftrace_run_update_code().
Another bug was discovered, that ftrace_startup_sysctl() called
ftrace_run_update_code() directly. If the function the ftrace_caller
trampoline changes, then it will not be updated. Instead a call
to ftrace_startup_enable() should be called because it tests to see
if the callback changed since the code was disabled, and will
tell the arch to update appropriately. Most archs do not need this
notification, but PowerPC does.
The problem could be seen by the following commands:
# echo 0 > /proc/sys/kernel/ftrace_enabled
# echo function > /sys/kernel/debug/tracing/current_tracer
# echo 1 > /proc/sys/kernel/ftrace_enabled
# cat /sys/kernel/debug/tracing/trace
The trace will show that function tracing was not active.
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/ftrace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2710,7 +2710,7 @@ static void ftrace_startup_sysctl(void)
command = FTRACE_UPDATE_CALLS;
if (ftrace_graph_active)
command |= FTRACE_START_FUNC_RET;
- ftrace_run_update_code(command);
+ ftrace_startup_enable(command);
}
}
@@ -5580,12 +5580,12 @@ ftrace_enable_sysctl(struct ctl_table *t
if (ftrace_enabled) {
- ftrace_startup_sysctl();
-
/* we are starting ftrace again */
if (ftrace_ops_list != &ftrace_list_end)
update_ftrace_function();
+ ftrace_startup_sysctl();
+
} else {
/* stopping ftrace calls (just send to ftrace_stub) */
ftrace_trace_function = ftrace_stub;
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-3.19/ftrace-clear-regs_en-and-tramp_en-flags-on-disabling-record-via-sysctl.patch
queue-3.19/ftrace-fix-en-dis-able-graph-caller-when-en-dis-abling-record-via-sysctl.patch
queue-3.19/ftrace-fix-ftrace-enable-ordering-of-sysctl-ftrace_enabled.patch
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