[patch 1/3] epoll cleanups - epoll include diet ...

[patch 1/3] epoll cleanups - epoll include diet ...

[Davide Libenzi]

Remove some unneeded include files from epoll code.


Signed-off-by: Davide Libenzi <davidel@xmailserver.org>


- Davide



Index: linux-2.6.21-rc5.mm4/fs/eventpoll.c
===================================================================
--- linux-2.6.21-rc5.mm4.orig/fs/eventpoll.c	2007-04-03 17:59:54.000000000 -0700
+++ linux-2.6.21-rc5.mm4/fs/eventpoll.c	2007-04-03 18:33:30.000000000 -0700
@@ -1,6 +1,6 @@
 /*
- *  fs/eventpoll.c ( Efficent event polling implementation )
- *  Copyright (C) 2001,...,2006	 Davide Libenzi
+ *  fs/eventpoll.c (Efficent event notification implementation)
+ *  Copyright (C) 2001,...,2007	 Davide Libenzi
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -17,30 +17,21 @@
 #include <linux/sched.h>
 #include <linux/fs.h>
 #include <linux/file.h>
-#include <linux/signal.h>
 #include <linux/errno.h>
-#include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
 #include <linux/string.h>
 #include <linux/list.h>
 #include <linux/hash.h>
 #include <linux/spinlock.h>
-#include <linux/syscalls.h>
 #include <linux/rwsem.h>
 #include <linux/rbtree.h>
 #include <linux/wait.h>
 #include <linux/eventpoll.h>
-#include <linux/mount.h>
-#include <linux/bitops.h>
 #include <linux/mutex.h>
 #include <linux/anon_inodes.h>
 #include <asm/uaccess.h>
-#include <asm/system.h>
-#include <asm/io.h>
-#include <asm/mman.h>
 #include <asm/atomic.h>
-#include <asm/semaphore.h>
 
 
 /*

Re: [patch 1/3] epoll cleanups - epoll include diet ...

[Andrew Morton]

On Tue, 03 Apr 2007 18:35:06 -0700
Davide Libenzi <davidel@xmailserver.org> wrote:

> Remove some unneeded include files from epoll code.
> 

Our definitions of "unneeded" might differ.

> 
> Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
> 
> 
> - Davide
> 
> 
> 
> Index: linux-2.6.21-rc5.mm4/fs/eventpoll.c
> ===================================================================
> --- linux-2.6.21-rc5.mm4.orig/fs/eventpoll.c	2007-04-03 17:59:54.000000000 -0700
> +++ linux-2.6.21-rc5.mm4/fs/eventpoll.c	2007-04-03 18:33:30.000000000 -0700
> @@ -1,6 +1,6 @@
>  /*
> - *  fs/eventpoll.c ( Efficent event polling implementation )
> - *  Copyright (C) 2001,...,2006	 Davide Libenzi
> + *  fs/eventpoll.c (Efficent event notification implementation)
> + *  Copyright (C) 2001,...,2007	 Davide Libenzi
>   *
>   *  This program is free software; you can redistribute it and/or modify
>   *  it under the terms of the GNU General Public License as published by
> @@ -17,30 +17,21 @@
>  #include <linux/sched.h>
>  #include <linux/fs.h>
>  #include <linux/file.h>
> -#include <linux/signal.h>
>  #include <linux/errno.h>
> -#include <linux/mm.h>
>  #include <linux/slab.h>
>  #include <linux/poll.h>
>  #include <linux/string.h>
>  #include <linux/list.h>
>  #include <linux/hash.h>
>  #include <linux/spinlock.h>
> -#include <linux/syscalls.h>
>  #include <linux/rwsem.h>
>  #include <linux/rbtree.h>
>  #include <linux/wait.h>
>  #include <linux/eventpoll.h>
> -#include <linux/mount.h>
> -#include <linux/bitops.h>
>  #include <linux/mutex.h>
>  #include <linux/anon_inodes.h>
>  #include <asm/uaccess.h>
> -#include <asm/system.h>
> -#include <asm/io.h>
> -#include <asm/mman.h>
>  #include <asm/atomic.h>
> -#include <asm/semaphore.h>

epoll uses signal stuff and might need signal.h.  It implements syscalls
and it certainly needs to have those syscall's prototypes in scope.  It
surely uses stuff from mm.h (doesn't everything??)

I am suspecting that this patch relies upon accidental nested inclusions
from within other headers.  But that is super-fragile: change a config
item, switch to a different architecture and whoops, it doesn't compile any
more.

Maybe I'm wrong, and you somehow worked out that none of these things which
these headers define, and none the things which these headers' includees
define is used in epoll.c or in the headers which are included after these
headers, or in those headers' includees.  If so, how the heck did you do
that?

Re: [patch 1/3] epoll cleanups - epoll include diet ...

[Davide Libenzi]

On Thu, 5 Apr 2007, Andrew Morton wrote:

> epoll uses signal stuff and might need signal.h.  It implements syscalls
> and it certainly needs to have those syscall's prototypes in scope.  It
> surely uses stuff from mm.h (doesn't everything??)

Ack about signal.h, I forgot about the pwait code :(
Why syscalls.h? The eventpoll.c file expots syscalls, but it doesn't use 
anything declared in there.
What does eventpoll.c use *directly* from mm.h? If eventpoll.c uses, let's 
say sched.h, and sched.h needs mm.h, it is sched.h responsibility to 
include the mm.h file not eventpoll.c one.



- Davide

Re: [patch 1/3] epoll cleanups - epoll include diet ...

[Andrew Morton]

On Thu, 5 Apr 2007 18:12:58 -0700 (PDT)
Davide Libenzi <davidel@xmailserver.org> wrote:

> On Thu, 5 Apr 2007, Andrew Morton wrote:
> 
> > epoll uses signal stuff and might need signal.h.  It implements syscalls
> > and it certainly needs to have those syscall's prototypes in scope.  It
> > surely uses stuff from mm.h (doesn't everything??)
> 
> Ack about signal.h, I forgot about the pwait code :(
> Why syscalls.h? The eventpoll.c file expots syscalls, but it doesn't use 
> anything declared in there.

So that the compiler can verify that our declarations of sys_epoll_foo()
match our definitions of them.

> What does eventpoll.c use *directly* from mm.h? If eventpoll.c uses, let's 
> say sched.h, and sched.h needs mm.h, it is sched.h responsibility to 
> include the mm.h file not eventpoll.c one.
> 

Sure.  But if epoll.c _does_ use something from mm.h (or uses something
from a header which mm.h includes) then if we later remove the #include
mm.h from sched.h, eventpoll.c will break.

The general rule is: include in .c the header files which provide the stuff
which that .c file uses.  Now, it maybe that eventpoll.c indeed uses nothing
which mm.h provides, and nothing which mm.h's includees provide.  But it is
non-trivial to prove that.  Once added, includes are hard to remove :(

Re: [patch 1/3] epoll cleanups - epoll include diet ...

[Davide Libenzi]

On Thu, 5 Apr 2007, Andrew Morton wrote:

> On Thu, 5 Apr 2007 18:12:58 -0700 (PDT)
> Davide Libenzi <davidel@xmailserver.org> wrote:
> 
> > On Thu, 5 Apr 2007, Andrew Morton wrote:
> > 
> > > epoll uses signal stuff and might need signal.h.  It implements syscalls
> > > and it certainly needs to have those syscall's prototypes in scope.  It
> > > surely uses stuff from mm.h (doesn't everything??)
> > 
> > Ack about signal.h, I forgot about the pwait code :(
> > Why syscalls.h? The eventpoll.c file expots syscalls, but it doesn't use 
> > anything declared in there.
> 
> So that the compiler can verify that our declarations of sys_epoll_foo()
> match our definitions of them.

Right. Just drop that patch then.



- Davide