From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Song Shuai <suagrfillet@gmail.com>
Subject: [for-next][PATCH 11/11] ftrace: Avoid needless updates of the ftrace function call
Date: Thu, 24 Nov 2022 09:50:30 -0500 [thread overview]
Message-ID: <20221124145046.999511177@goodmis.org> (raw)
In-Reply-To: 20221124145019.782980678@goodmis.org
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Song Shuai reported:
The list func (ftrace_ops_list_func) will be patched first
before the transition between old and new calls are set,
which fixed the race described in this commit `59338f75`.
While ftrace_trace_function changes from the list func to a
ftrace_ops func, like unregistering the klp_ops to leave the only
global_ops in ftrace_ops_list, the ftrace_[regs]_call will be
replaced with the list func although it already exists. So there
should be a condition to avoid this.
And suggested using another variable to keep track of what the ftrace
function is set to. But this could be simplified by using a helper
function that does the same with a static variable.
Link: https://lore.kernel.org/lkml/20221026132039.2236233-1-suagrfillet@gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20221122180905.737b6f52@gandalf.local.home
Reported-by: Song Shuai <suagrfillet@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 65a5d36463e0..d04552c0c275 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2763,6 +2763,19 @@ void __weak ftrace_arch_code_modify_post_process(void)
{
}
+static int update_ftrace_func(ftrace_func_t func)
+{
+ static ftrace_func_t save_func;
+
+ /* Avoid updating if it hasn't changed */
+ if (func == save_func)
+ return 0;
+
+ save_func = func;
+
+ return ftrace_update_ftrace_func(func);
+}
+
void ftrace_modify_all_code(int command)
{
int update = command & FTRACE_UPDATE_TRACE_FUNC;
@@ -2783,7 +2796,7 @@ void ftrace_modify_all_code(int command)
* traced.
*/
if (update) {
- err = ftrace_update_ftrace_func(ftrace_ops_list_func);
+ err = update_ftrace_func(ftrace_ops_list_func);
if (FTRACE_WARN_ON(err))
return;
}
@@ -2799,7 +2812,7 @@ void ftrace_modify_all_code(int command)
/* If irqs are disabled, we are in stop machine */
if (!irqs_disabled())
smp_call_function(ftrace_sync_ipi, NULL, 1);
- err = ftrace_update_ftrace_func(ftrace_trace_function);
+ err = update_ftrace_func(ftrace_trace_function);
if (FTRACE_WARN_ON(err))
return;
}
--
2.35.1
prev parent reply other threads:[~2022-11-24 14:51 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-24 14:50 [for-next][PATCH 00/11] tracing: Updates for 6.2 Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 01/11] ftrace: Clean comments related to FTRACE_OPS_FL_PER_CPU Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 02/11] tracing: Add __cpumask to denote a trace event field that is a cpumask_t Steven Rostedt
2022-12-12 14:53 ` Douglas Raillard
2022-12-12 16:12 ` Steven Rostedt
2022-12-12 17:04 ` Steven Rostedt
2022-12-12 22:19 ` Douglas Raillard
2022-12-12 23:53 ` Steven Rostedt
2022-12-13 14:20 ` Douglas Raillard
2022-12-13 15:11 ` Steven Rostedt
2022-12-13 17:40 ` Douglas Raillard
2022-12-13 19:44 ` Steven Rostedt
2022-12-13 21:14 ` Douglas Raillard
2022-12-13 19:50 ` Douglas Raillard
2022-11-24 14:50 ` [for-next][PATCH 03/11] tracing: Add trace_trigger kernel command line option Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 04/11] ring_buffer: Remove unused "event" parameter Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 05/11] tracing/osnoise: Add osnoise/options file Steven Rostedt
2022-11-24 17:31 ` Daniel Bristot de Oliveira
2022-11-24 19:28 ` Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 06/11] tracing/osnoise: Add OSNOISE_WORKLOAD option Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 07/11] Documentation/osnoise: Add osnoise/options documentation Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 08/11] tracing/perf: Use strndup_user instead of kzalloc/strncpy_from_user Steven Rostedt
2022-11-24 14:50 ` [for-next][PATCH 09/11] tracing: Make tracepoint_print_iter static Steven Rostedt
2022-11-24 14:50 ` Steven Rostedt [this message]
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