[PATCH 6.18 042/212] fgraph: Fix thresh_return nosleeptime double-adjust

Greg Kroah-Hartman
2026-03-23T14:02:57Z

From: Shengming Hu <hu.shengming@zte.com.cn>

[ Upstream commit b96d0c59cdbb2a22b2545f6f3d5c6276b05761dd ]

trace_graph_thresh_return() called handle_nosleeptime() and then delegated
to trace_graph_return(), which calls handle_nosleeptime() again. When
sleep-time accounting is disabled this double-adjusts calltime and can
produce bogus durations (including underflow).

Fix this by computing rettime once, applying handle_nosleeptime() only
once, using the adjusted calltime for threshold comparison, and writing
the return event directly via __trace_graph_return() when the threshold is
met.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260221113314048jE4VRwIyZEALiYByGK0My@zte.com.cn
Fixes: 3c9880f3ab52b ("ftrace: Use a running sleeptime instead of saving on shadow stack")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/trace/trace_functions_graph.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -378,9 +378,14 @@ static void trace_graph_thresh_return(st
struct fgraph_ops *gops,
struct ftrace_regs *fregs)
{
+ struct trace_array *tr = gops->private;
struct fgraph_times *ftimes;
+ unsigned int trace_ctx;
+ u64 calltime, rettime;
int size;

+ rettime = trace_clock_local();
+
ftrace_graph_addr_finish(gops, trace);

if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
@@ -394,11 +399,13 @@ static void trace_graph_thresh_return(st

handle_nosleeptime(trace, ftimes, size);

- if (tracing_thresh &&
- (trace_clock_local() - ftimes->calltime < tracing_thresh))
+ calltime = ftimes->calltime;
+
+ if (tracing_thresh && (rettime - calltime < tracing_thresh))
return;
- else
- trace_graph_return(trace, gops, fregs);
+
+ trace_ctx = tracing_gen_ctx();
+ __trace_graph_return(tr, trace, trace_ctx, calltime, rettime);
}

static struct fgraph_ops funcgraph_ops = {