linux-kernel - Re: [PATCH v2] ftrace/module: Move ftrace_release_mod to ddebug

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Date:   Thu, 28 Dec 2017 11:32:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     Namit Gupta <gupta.namit@...sung.com>, mingo@...hat.com,
        linux-kernel@...r.kernel.org, pankaj.m@...sung.com,
        a.sahrawat@...sung.com, rusty@...tcorp.com.au
Subject: Re: [PATCH v2] ftrace/module: Move ftrace_release_mod to
 ddebug_cleanup label


Jessica,

Can you take this patch. You can add:

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Thanks!

-- Steve


On Tue, 12 Dec 2017 17:24:32 +0530
Namit Gupta <gupta.namit@...sung.com> wrote:

> ftrace_module_init happen after dynamic_debug_setup, it is desired that
> cleanup should be called after this label however in current implementation
> it is called in free module label,ie:even though ftrace in not initialized,
> from so many fail case ftrace_release_mod() will be called and unnecessary
> traverse the whole list.
> In below patch we moved ftrace_release_mod() from free_module label to
> ddebug_cleanup label. that is the best possible location, other solution
> is to make new label to ftrace_release_mod() but since ftrace_module_init()
> is not return with minimum changes it should be in ddebug_cleanup label.
> 
> 
> Signed-off-by: Namit Gupta <gupta.namit@...sung.com>
> 
> ---
>  kernel/module.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 0d1cb8d..4be966a 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3523,6 +3523,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	unset_module_core_ro_nx(mod);
>  
>   ddebug_cleanup:
> +	ftrace_release_mod(mod);
>  	dynamic_debug_remove(info->debug);
>  	synchronize_sched();
>  	kfree(mod->args);
> @@ -3541,12 +3542,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	synchronize_rcu();
>  	mutex_unlock(&module_mutex);
>   free_module:
> -	/*
> -	 * Ftrace needs to clean up what it initialized.
> -	 * This does nothing if ftrace_module_init() wasn't called,
> -	 * but it must be called outside of module_mutex.
> -	 */
> -	ftrace_release_mod(mod);
>  	/* Free lock-classes; relies on the preceding sync_rcu() */
>  	lockdep_free_key_range(mod->module_core, mod->core_size);
>