* atomic_t (24 bits???)
@ 2003-02-25 19:11 Richard B. Johnson
2003-02-25 19:14 ` Roman Zippel
2003-02-25 19:17 ` Daniel Jacobowitz
0 siblings, 2 replies; 6+ messages in thread
From: Richard B. Johnson @ 2003-02-25 19:11 UTC (permalink / raw)
To: Linux kernel
In ../linux/include/asm/atomic.h, for versions 2.4.18 and
above as far as I've checked, there are repeated warnings
"Note that the guaranteed useful range of an atomic_t is
only 24 bits."
I fail to see any reason why as atomic_t is typdefed to a
volatile int which, on ix86 seems to be 32 bits.
Does anybody know if this is just some old comments from a
previous atomic_t type of, perhaps, char[3]?
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: atomic_t (24 bits???)
2003-02-25 19:11 atomic_t (24 bits???) Richard B. Johnson
@ 2003-02-25 19:14 ` Roman Zippel
2003-02-25 19:31 ` Richard B. Johnson
2003-02-25 19:17 ` Daniel Jacobowitz
1 sibling, 1 reply; 6+ messages in thread
From: Roman Zippel @ 2003-02-25 19:14 UTC (permalink / raw)
To: Richard B. Johnson; +Cc: Linux kernel
Hi,
On Tue, 25 Feb 2003, Richard B. Johnson wrote:
> In ../linux/include/asm/atomic.h, for versions 2.4.18 and
> above as far as I've checked, there are repeated warnings
> "Note that the guaranteed useful range of an atomic_t is
> only 24 bits."
>
> I fail to see any reason why as atomic_t is typdefed to a
> volatile int which, on ix86 seems to be 32 bits.
>
> Does anybody know if this is just some old comments from a
> previous atomic_t type of, perhaps, char[3]?
include/asm-sparc/atomic.h
bye, Roman
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: atomic_t (24 bits???)
2003-02-25 19:11 atomic_t (24 bits???) Richard B. Johnson
2003-02-25 19:14 ` Roman Zippel
@ 2003-02-25 19:17 ` Daniel Jacobowitz
2003-02-25 19:31 ` Richard B. Johnson
2003-02-25 21:57 ` Russell King
1 sibling, 2 replies; 6+ messages in thread
From: Daniel Jacobowitz @ 2003-02-25 19:17 UTC (permalink / raw)
To: Richard B. Johnson; +Cc: Linux kernel
On Tue, Feb 25, 2003 at 02:11:11PM -0500, Richard B. Johnson wrote:
>
> In ../linux/include/asm/atomic.h, for versions 2.4.18 and
> above as far as I've checked, there are repeated warnings
> "Note that the guaranteed useful range of an atomic_t is
> only 24 bits."
>
> I fail to see any reason why as atomic_t is typdefed to a
> volatile int which, on ix86 seems to be 32 bits.
>
> Does anybody know if this is just some old comments from a
> previous atomic_t type of, perhaps, char[3]?
There are other platforms where you can't reliably use the whole word.
Some ARM atomic_t implementations are like this, although I don't know
if the one in the kernel is.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: atomic_t (24 bits???)
2003-02-25 19:14 ` Roman Zippel
@ 2003-02-25 19:31 ` Richard B. Johnson
0 siblings, 0 replies; 6+ messages in thread
From: Richard B. Johnson @ 2003-02-25 19:31 UTC (permalink / raw)
To: Roman Zippel; +Cc: Linux kernel
On Tue, 25 Feb 2003, Roman Zippel wrote:
> Hi,
>
> On Tue, 25 Feb 2003, Richard B. Johnson wrote:
>
> > In ../linux/include/asm/atomic.h, for versions 2.4.18 and
> > above as far as I've checked, there are repeated warnings
> > "Note that the guaranteed useful range of an atomic_t is
> > only 24 bits."
> >
> > I fail to see any reason why as atomic_t is typdefed to a
> > volatile int which, on ix86 seems to be 32 bits.
> >
> > Does anybody know if this is just some old comments from a
> > previous atomic_t type of, perhaps, char[3]?
>
> include/asm-sparc/atomic.h
>
> bye, Roman
>
Thank you.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: atomic_t (24 bits???)
2003-02-25 19:17 ` Daniel Jacobowitz
@ 2003-02-25 19:31 ` Richard B. Johnson
2003-02-25 21:57 ` Russell King
1 sibling, 0 replies; 6+ messages in thread
From: Richard B. Johnson @ 2003-02-25 19:31 UTC (permalink / raw)
To: Daniel Jacobowitz; +Cc: Linux kernel
On Tue, 25 Feb 2003, Daniel Jacobowitz wrote:
> On Tue, Feb 25, 2003 at 02:11:11PM -0500, Richard B. Johnson wrote:
> >
> > In ../linux/include/asm/atomic.h, for versions 2.4.18 and
> > above as far as I've checked, there are repeated warnings
> > "Note that the guaranteed useful range of an atomic_t is
> > only 24 bits."
> >
> > I fail to see any reason why as atomic_t is typdefed to a
> > volatile int which, on ix86 seems to be 32 bits.
> >
> > Does anybody know if this is just some old comments from a
> > previous atomic_t type of, perhaps, char[3]?
>
> There are other platforms where you can't reliably use the whole word.
> Some ARM atomic_t implementations are like this, although I don't know
> if the one in the kernel is.
>
> --
> Daniel Jacobowitz
> MontaVista Software Debian GNU/Linux Developer
>
Okay. Thanks.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: atomic_t (24 bits???)
2003-02-25 19:17 ` Daniel Jacobowitz
2003-02-25 19:31 ` Richard B. Johnson
@ 2003-02-25 21:57 ` Russell King
1 sibling, 0 replies; 6+ messages in thread
From: Russell King @ 2003-02-25 21:57 UTC (permalink / raw)
To: Linux kernel
On Tue, Feb 25, 2003 at 02:17:11PM -0500, Daniel Jacobowitz wrote:
> There are other platforms where you can't reliably use the whole word.
> Some ARM atomic_t implementations are like this, although I don't know
> if the one in the kernel is.
The ARM atomic_t isn't 24-bit - it's a full paid up member of the
32-bit club. 8)
--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html
^ permalink raw reply [flat|nested] 6+ messages in thread
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2003-02-25 19:11 atomic_t (24 bits???) Richard B. Johnson
2003-02-25 19:14 ` Roman Zippel
2003-02-25 19:31 ` Richard B. Johnson
2003-02-25 19:17 ` Daniel Jacobowitz
2003-02-25 19:31 ` Richard B. Johnson
2003-02-25 21:57 ` Russell King
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