linux-kernel - Re: [PATCH] ftrace: Remove unused global 'ftrace_direct_func

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Date: Mon, 6 May 2024 23:35:50 +0000
From: "Dr. David Alan Gilbert" <linux@...blig.org>
To: rostedt@...dmis.org, mhiramat@...nel.org
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: Remove unused global 'ftrace_direct_func_count'

* linux@...blig.org (linux@...blig.org) wrote:
> From: "Dr. David Alan Gilbert" <linux@...blig.org>
> 
> Commit 8788ca164eb4b ("ftrace: Remove the legacy _ftrace_direct API")
> stopped setting the 'ftrace_direct_func_count' variable, but left
> it around.  Clean it up.
> 
> Signed-off-by: Dr. David Alan Gilbert <linux@...blig.org>

FYI this is on top of my earlier 'ftrace: Remove unused list 'ftrace_direct_funcs'

Dave

> ---
>  include/linux/ftrace.h |  2 --
>  kernel/trace/fgraph.c  | 11 -----------
>  kernel/trace/ftrace.c  |  1 -
>  3 files changed, 14 deletions(-)
> 
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index b01cca36147ff..e3a83ebd1b333 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -413,7 +413,6 @@ struct ftrace_func_entry {
>  };
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> -extern int ftrace_direct_func_count;
>  unsigned long ftrace_find_rec_direct(unsigned long ip);
>  int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr);
>  int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr,
> @@ -425,7 +424,6 @@ void ftrace_stub_direct_tramp(void);
>  
>  #else
>  struct ftrace_ops;
> -# define ftrace_direct_func_count 0
>  static inline unsigned long ftrace_find_rec_direct(unsigned long ip)
>  {
>  	return 0;
> diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> index c83c005e654e3..a130b2d898f7c 100644
> --- a/kernel/trace/fgraph.c
> +++ b/kernel/trace/fgraph.c
> @@ -125,17 +125,6 @@ int function_graph_enter(unsigned long ret, unsigned long func,
>  {
>  	struct ftrace_graph_ent trace;
>  
> -#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> -	/*
> -	 * Skip graph tracing if the return location is served by direct trampoline,
> -	 * since call sequence and return addresses are unpredictable anyway.
> -	 * Ex: BPF trampoline may call original function and may skip frame
> -	 * depending on type of BPF programs attached.
> -	 */
> -	if (ftrace_direct_func_count &&
> -	    ftrace_find_rec_direct(ret - MCOUNT_INSN_SIZE))
> -		return -EBUSY;
> -#endif
>  	trace.func = func;
>  	trace.depth = ++current->curr_ret_depth;
>  
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index b18b4ece3d7c9..adf34167c3418 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2538,7 +2538,6 @@ ftrace_find_unique_ops(struct dyn_ftrace *rec)
>  /* Protected by rcu_tasks for reading, and direct_mutex for writing */
>  static struct ftrace_hash __rcu *direct_functions = EMPTY_HASH;
>  static DEFINE_MUTEX(direct_mutex);
> -int ftrace_direct_func_count;
>  
>  /*
>   * Search the direct_functions hash to see if the given instruction pointer
> -- 
> 2.45.0
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/