6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ye Weihua [ Upstream commit edede7a6dcd7435395cf757d053974aaab6ab1c2 ] This warning was triggered during testing on v6.16: notifier callback ftrace_suspend_notifier_call already registered WARNING: CPU: 2 PID: 86 at kernel/notifier.c:23 notifier_chain_register+0x44/0xb0 ... Call Trace: blocking_notifier_chain_register+0x34/0x60 register_ftrace_graph+0x330/0x410 ftrace_profile_write+0x1e9/0x340 vfs_write+0xf8/0x420 ? filp_flush+0x8a/0xa0 ? filp_close+0x1f/0x30 ? do_dup2+0xaf/0x160 ksys_write+0x65/0xe0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f When writing to the function_profile_enabled interface, the notifier was not unregistered after start_graph_tracing failed, causing a warning the next time function_profile_enabled was written. Fixed by adding unregister_pm_notifier in the exception path. Link: https://lore.kernel.org/20250818073332.3890629-1-yeweihua4@huawei.com Fixes: 4a2b8dda3f870 ("tracing/function-graph-tracer: fix a regression while suspend to disk") Acked-by: Masami Hiramatsu (Google) Signed-off-by: Ye Weihua Signed-off-by: Steven Rostedt (Google) Signed-off-by: Sasha Levin --- kernel/trace/fgraph.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index c83c005e654e3..f7e0ade90500c 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -648,6 +648,7 @@ int register_ftrace_graph(struct fgraph_ops *gops) ret = start_graph_tracing(); if (ret) { ftrace_graph_active--; + unregister_pm_notifier(&ftrace_suspend_notifier); goto out; } -- 2.53.0