linux-kernel - Re: [PATCH] fgraph: Fix missing unlock in register_ftrace

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Message-ID: <49d1672e-71e2-dc87-1fb3-cde430e0339f@huawei.com>
Date: Thu, 24 Oct 2024 10:45:46 +0800
From: Li Huafei <lihuafei1@...wei.com>
To: Steven Rostedt <rostedt@...dmis.org>
CC: <dan.carpenter@...aro.org>, <mhiramat@...nel.org>,
	<linux-kernel@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>,
	<oe-kbuild@...ts.linux.dev>, <lkp@...el.com>
Subject: Re: [PATCH] fgraph: Fix missing unlock in register_ftrace_graph()

Hi Steve,

On 2024/10/23 17:29, Steven Rostedt wrote:
> On Thu, 24 Oct 2024 01:04:48 +0800
> Li Huafei <lihuafei1@...wei.com> wrote:
> 
>> Instead of returning an error, goto the mutex unlock at the end of the
>> function.
>>
>> Fixes smatch warning:
>>
>> kernel/trace/fgraph.c:1317 register_ftrace_graph() warn: inconsistent returns '&ftrace_lock'.
>>
>> Fixes: 2c02f7375e65 ("fgraph: Use CPU hotplug mechanism to initialize idle shadow stacks")
>> Reported-by: kernel test robot <lkp@...el.com>
>> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
>> Closes: https://lore.kernel.org/r/202410220121.wxg0olfd-lkp@intel.com/
>> Signed-off-by: Li Huafei <lihuafei1@...wei.com>
>> ---
>>  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 41e7a15dcb50..98fa7b2a4903 100644
>> --- a/kernel/trace/fgraph.c
>> +++ b/kernel/trace/fgraph.c
>> @@ -1259,7 +1259,7 @@ int register_ftrace_graph(struct fgraph_ops *gops)
>>  					fgraph_cpu_init, NULL);
>>  		if (ret < 0) {
>>  			pr_warn("fgraph: Error to init cpu hotplug support\n");
>> -			return ret;
>> +			goto out;
>>  		}
>>  		fgraph_initialized = true;
>>  		ret = 0;
> 
> Actually, I'm thinking we just should use guard(mutex)(&ftrace_lock);
> 

Agreed, this will make the code simpler and avoid mistakes. If we need
to replace all mutex(&ftrace_lock), would it be better to submit another
cleanup patch? We can fix the issue here first.

Thanks,
Huafei

> -- Steve
> 
> .
>