| From 2e9abcac56998259d594c99d80c38f5a230d3c4d Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Fri, 13 Feb 2026 14:29:32 +0800 |
| Subject: function_graph: Restore direct mode when callbacks drop to one |
| |
| From: Shengming Hu <hu.shengming@zte.com.cn> |
| |
| [ Upstream commit 53b2fae90ff01fede6520ca744ed5e8e366497ba ] |
| |
| When registering a second fgraph callback, direct path is disabled and |
| array loop is used instead. When ftrace_graph_active falls back to one, |
| we try to re-enable direct mode via ftrace_graph_enable_direct(true, ...). |
| But ftrace_graph_enable_direct() incorrectly disables the static key |
| rather than enabling it. This leaves fgraph_do_direct permanently off |
| after first multi-callback transition, so direct fast mode is never |
| restored. |
| |
| Cc: stable@vger.kernel.org |
| Link: https://patch.msgid.link/20260213142932519cuWSpEXeS4-UnCvNXnK2P@zte.com.cn |
| Fixes: cc60ee813b503 ("function_graph: Use static_call and branch to optimize entry function") |
| Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn> |
| Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| kernel/trace/fgraph.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c |
| index 599f2939cd940..13832ff06c96c 100644 |
| --- a/kernel/trace/fgraph.c |
| +++ b/kernel/trace/fgraph.c |
| @@ -1311,7 +1311,7 @@ static void ftrace_graph_enable_direct(bool enable_branch, struct fgraph_ops *go |
| static_call_update(fgraph_func, func); |
| static_call_update(fgraph_retfunc, retfunc); |
| if (enable_branch) |
| - static_branch_disable(&fgraph_do_direct); |
| + static_branch_enable(&fgraph_do_direct); |
| } |
| |
| static void ftrace_graph_disable_direct(bool disable_branch) |
| -- |
| 2.51.0 |
| |
