linux-kernel - Re: [PATCH 00/16 v3] tracing: Add new file system tracefs

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Message-ID: <20150127044625.GX29656@ZenIV.linux.org.uk>
Date:	Tue, 27 Jan 2015 04:46:25 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 00/16 v3] tracing: Add new file system tracefs

On Mon, Jan 26, 2015 at 09:34:19PM -0500, Steven Rostedt wrote:
> On Mon, 26 Jan 2015 18:37:39 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> 
> > > the first call of tracing_init_dentry().  Prior to that it's NULL.
> > > BTW, may I politely inquire what the fuck are those contortions in
> > > tracing_init_dentry_tr() about?  Looks like a stunningly convoluted
> > > way to trigger that automount point creation early in
> > > tracer_init_tracefs(). Why not do that right there explicitly?
> > 
> > Yeah, that could be cleaned up. Before the tracefs code, it made much
> > more sense to keep that as a single function. Now that
> > global_array.dir is treated differently as the subdirs, it does make
> > sense to have global_arry.dir initialized in a separate function.
> > 
> > I'll update my patch series to do this.
> 
> Now I remember why I did this (as I changed the code and everything
> blew up). The files in the tracing directory can be created by several
> users (do a grep for fs_initcall() in kernel/trace/*.c). The first
> caller to add a file initializes the tracing directory.
> 
> I guess I can have all the other callers use fs_initcall_sync(). I'm
> assuming those come after fs_initcall().

Ah...  That explains some of the oddities of that kind (not all of them,
though - your trace_options_init_dentry() is called by
create_trace_option_dirs() and create_trace_option_core_file(), which is
called only by create_trace_option_dirs(), and that - quite a few times,
each time calling trace_options_init_dentry()).

Strange style, IMO.  Frankly, I'd rather have the ordering as explicit as it
gets...
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