Re: [PATCH for review] [12/48] x86_64: use the global PIT lock

From: Dmitry Torokhov
Date: Fri Jul 20 2007 - 08:50:39 EST


On 7/20/07, Andi Kleen <ak@xxxxxxx> wrote:

> +static DEFINE_SPINLOCK(i8253_lock);
> +
> static __init int add_pcspkr(void)
> {
> struct platform_device *pd;
> @@ -1501,9 +1503,14 @@ static __init int add_pcspkr(void)
> if (!pd)
> return -ENOMEM;
>
> +pd->dev.platform_data = &i8253_lock;

That seems pretty ugly to pass spinlocks around in void * pointers.

That spinlock _is_ platform data. We could define

struct pcspkr_platform_data {
spinlock_t *lock;
};

and pass around this as the rest of platform code does but then we'd
need a header file and it would add a level of indirection but if you
like this better I can change it. Otherwise spinlock is another data
structure and we pass them around all teh time.

Also
out of general memory bloat reasons i don't like allocating big data structures
just for this.


I am not sure where you see new data structure allocation... If you
look at your box you should see that /sys/bus/platform/devices/pcspkr
device is already there. We already create it so that pcspkr driver
can bind to it.

Wouldn't it be better to just define i8253_lock weakly in the pcspkr code and let
the architecture override it?

Yes, it probably is btetter.


> Index: work/arch/x86_64/kernel/time.c
> ===================================================================
> --- work.orig/arch/x86_64/kernel/time.c
> +++ work/arch/x86_64/kernel/time.c
> @@ -23,6 +23,7 @@
> #include <linux/module.h>
> #include <linux/device.h>
> #include <linux/sysdev.h>
> +#include <linux/platform_device.h>
> #include <linux/bcd.h>
> #include <linux/notifier.h>
> #include <linux/cpu.h>
> @@ -185,7 +186,7 @@ void main_timer_handler(void)
> set_rtc_mmss(xtime.tv_sec);
> rtc_update = xtime.tv_sec + 660;
> }
> -
> +
> write_sequnlock(&xtime_lock);
> }

No random white space changes in patches, multiple occurrences ?!?


By bad, sorry.

--
Dmitry
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