From: <[email protected]>
Cc: <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>
Unify the spinlock initialization as far as possible.
Signed-off-by: Amit Gud <[email protected]>
Signed-off-by: Domen Puncer <[email protected]>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
---
linux-2.6.11-paolo/arch/um/drivers/port_kern.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)
diff -puN arch/um/drivers/port_kern.c~uml-switch-spinlock-init arch/um/drivers/port_kern.c
--- linux-2.6.11/arch/um/drivers/port_kern.c~uml-switch-spinlock-init 2005-03-09 10:35:28.786848080 +0100
+++ linux-2.6.11-paolo/arch/um/drivers/port_kern.c 2005-03-09 10:35:28.789847624 +0100
@@ -185,11 +185,11 @@ void *port_data(int port_num)
.has_connection = 0,
.sem = __SEMAPHORE_INITIALIZER(port->sem,
0),
- .lock = SPIN_LOCK_UNLOCKED,
.port = port_num,
.fd = fd,
.pending = LIST_HEAD_INIT(port->pending),
.connections = LIST_HEAD_INIT(port->connections) });
+ spin_lock_init(&port->lock);
list_add(&port->list, &ports);
found:
_
On Wed, Mar 09, 2005 at 10:42:33AM +0100, [email protected] wrote:
>
> From: <[email protected]>
> Cc: <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>
>
> Unify the spinlock initialization as far as possible.
Are you sure this is really the best option in this instance?
Sometimes, static data initialisation is more efficient than
code-based manual initialisation, especially when the memory
is written to anyway.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
Russell King <[email protected]> wrote:
>
> I'm not convinced about the practicality of converting all static
> initialisations to code-based initialisations though
This is the first one I recall seeing. All the other conversions were replacing
static spinlock_t lock = SPIN_LOCK_UNLOCKED;
with
static DEFINE_SPINLOCK(lock);
and replacing
{
lock = SPIN_LOCK_UNLOCKED;
}
with
{
spin_lock_init(lock);
}
On Wed, 9 Mar 2005, Andrew Morton wrote:
> Russell King <[email protected]> wrote:
>>
>> I'm not convinced about the practicality of converting all static
>> initialisations to code-based initialisations though
>
> This is the first one I recall seeing. All the other conversions were replacing
>
> static spinlock_t lock = SPIN_LOCK_UNLOCKED;
>
> with
> static DEFINE_SPINLOCK(lock);
>
> and replacing
>
> {
> lock = SPIN_LOCK_UNLOCKED;
> }
>
> with
>
> {
> spin_lock_init(lock);
> }
We need to retain the spin_lock_init(&lock) because not all spin-locks
are allocated at compile-time. They might be allocated from kmalloc()
on startup, probably in a structure, along with other so-called
global data.
Cheers,
Dick Johnson
Penguin : Linux version 2.6.10 on an i686 machine (5537.79 BogoMips).
Notice : All mail here is now cached for review by Dictator Bush.
98.36% of all statistics are fiction.
On Wed, 9 Mar 2005, linux-os wrote:
> We need to retain the spin_lock_init(&lock) because not all spin-locks
> are allocated at compile-time. They might be allocated from kmalloc()
> on startup, probably in a structure, along with other so-called
> global data.
Not to worry my good man, it's not going anywhere.
On Wed, Mar 09, 2005 at 08:52:24PM +0100, Blaisorblade wrote:
> On Wednesday 09 March 2005 18:12, Russell King wrote:
> > On Wed, Mar 09, 2005 at 10:42:33AM +0100, [email protected] wrote:
> > > From: <[email protected]>
> > > Cc: <[email protected]>, <[email protected]>,
> > > <[email protected]>, <[email protected]>
> > >
> > > Unify the spinlock initialization as far as possible.
>
> > Are you sure this is really the best option in this instance?
> > Sometimes, static data initialisation is more efficient than
> > code-based manual initialisation, especially when the memory
> > is written to anyway.
> Agreed, theoretically, but this was done for multiple reasons globally, for
> instance as a preparation to Ingo Molnar's preemption patches. There was
> mention of this on lwn.net about this:
>
> http://lwn.net/Articles/108719/
Was this announced on linux-kernel as well? I don't remember seeing it.
I'm not convinced about the practicality of converting all static
initialisations to code-based initialisations though - I can see
that the number of initialisation functions scattered throughout
the kernel is going to increase dramatically to achieve this.
With a 2.4 to 2.6 kernel bloat already on the order of 140% for
similar functionality, I can only see the kernel getting more and
more bloated _for the same feature level_ because we're trying to
add more features to the kernel.
I'm not entirely convinced that is an all round sane approach.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
On Wednesday 09 March 2005 18:12, Russell King wrote:
> On Wed, Mar 09, 2005 at 10:42:33AM +0100, [email protected] wrote:
> > From: <[email protected]>
> > Cc: <[email protected]>, <[email protected]>,
> > <[email protected]>, <[email protected]>
> >
> > Unify the spinlock initialization as far as possible.
> Are you sure this is really the best option in this instance?
> Sometimes, static data initialisation is more efficient than
> code-based manual initialisation, especially when the memory
> is written to anyway.
Agreed, theoretically, but this was done for multiple reasons globally, for
instance as a preparation to Ingo Molnar's preemption patches. There was
mention of this on lwn.net about this:
http://lwn.net/Articles/108719/
Ok?
--
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade
On Wed, 2005-03-09 at 20:52 +0100, Blaisorblade wrote:
> > Are you sure this is really the best option in this instance?
> > Sometimes, static data initialisation is more efficient than
> > code-based manual initialisation, especially when the memory
> > is written to anyway.
> Agreed, theoretically, but this was done for multiple reasons globally, for
> instance as a preparation to Ingo Molnar's preemption patches. There was
> mention of this on lwn.net about this:
>
> http://lwn.net/Articles/108719/
Those patches did only the conversion of
static spinlock_t lock = SPIN_LOCK_UNLOCKED;
lock = SPIN_LOCK_UNLOCKED;
to
static DEFINE_SPINLOCK(lock);
spin_lock_init(lock);
If you want to do static initialization inside of structures, then you
have to define a seperate MACRO similar to the static initialization of
list_head's inside of structures:
static struct sysfs_dirent sysfs_root = {
.s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling),
tglx
On Thursday 10 March 2005 09:12, Thomas Gleixner wrote:
> On Wed, 2005-03-09 at 20:52 +0100, Blaisorblade wrote:
> > > Are you sure this is really the best option in this instance?
> > > Sometimes, static data initialisation is more efficient than
> > > code-based manual initialisation, especially when the memory
> > > is written to anyway.
> >
> > Agreed, theoretically, but this was done for multiple reasons globally,
> > for instance as a preparation to Ingo Molnar's preemption patches. There
> > was mention of this on lwn.net about this:
> >
> > http://lwn.net/Articles/108719/
>
> Those patches did only the conversion of
>
> static spinlock_t lock = SPIN_LOCK_UNLOCKED;
> lock = SPIN_LOCK_UNLOCKED;
> to
> static DEFINE_SPINLOCK(lock);
> spin_lock_init(lock);
First: I didn't write the patch, only forwarded it, so I just guessed why it
was done.
The latter is spin_lock_init(&lock); (since someone got confused about this).
However, this is a .lock = SPIN_LOCK_UNLOCKED ->
spin_lock_init(&struct.lock),
so I don't understand what changes... the structure is initialized inside a
function, so there's no change.
> If you want to do static initialization inside of structures, then you
> have to define a seperate MACRO similar to the static initialization of
> list_head's inside of structures:
> static struct sysfs_dirent sysfs_root = {
> .s_sibling = LIST_HEAD_INIT(sysfs_root.s_sibling),
I don't see the need here... and the initialization is not in static code; it
changes this code snippet:
void *port_data(int port_num)
{
//...
*port = ((struct port_list)
{ .list = LIST_HEAD_INIT(port->list),
.has_connection = 0,
.sem = __SEMAPHORE_INITIALIZER(port->sem,
0),
.lock = SPIN_LOCK_UNLOCKED,
.port = port_num,
.fd = fd,
.pending = LIST_HEAD_INIT(port->pending),
.connections =
LIST_HEAD_INIT(port->connections) });
So you are all doing some confusion (in fact I guess Andrew realized this when
he merged this anyway).
--
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade