* backwards busy wait using "time_before()"??
@ 2009-12-31 16:40 Robert P. J. Day
2009-12-31 19:23 ` Robert P. J. Day
2010-01-01 15:17 ` Andi Kleen
0 siblings, 2 replies; 3+ messages in thread
From: Robert P. J. Day @ 2009-12-31 16:40 UTC (permalink / raw)
To: Linux Kernel Mailing List
if this is an idiotic question, i'll blame it on the fact that
there's only decaf left in the house.
from drivers/spi/spi_stmp.c:
#define busy_wait(cond) \
({ \
unsigned long end_jiffies = jiffies + STMP_SPI_TIMEOUT; \
bool succeeded = false; \
do { \
if (cond) { \
succeeded = true; \
break; \
} \
cpu_relax(); \
} while (time_before(end_jiffies, jiffies)); \
succeeded; \
})
is it just me, or do those arguments to time_before() look
backwards?
rday
--
========================================================================
Robert P. J. Day Waterloo, Ontario, CANADA
Linux Consulting, Training and Kernel Pedantry.
Web page: http://crashcourse.ca
Twitter: http://twitter.com/rpjday
========================================================================
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: backwards busy wait using "time_before()"??
2009-12-31 16:40 backwards busy wait using "time_before()"?? Robert P. J. Day
@ 2009-12-31 19:23 ` Robert P. J. Day
2010-01-01 15:17 ` Andi Kleen
1 sibling, 0 replies; 3+ messages in thread
From: Robert P. J. Day @ 2009-12-31 19:23 UTC (permalink / raw)
To: Linux Kernel Mailing List
On Thu, 31 Dec 2009, Robert P. J. Day wrote:
>
> if this is an idiotic question, i'll blame it on the fact that
> there's only decaf left in the house.
>
> from drivers/spi/spi_stmp.c:
>
> #define busy_wait(cond) \
> ({ \
> unsigned long end_jiffies = jiffies + STMP_SPI_TIMEOUT; \
> bool succeeded = false; \
> do { \
> if (cond) { \
> succeeded = true; \
> break; \
> } \
> cpu_relax(); \
> } while (time_before(end_jiffies, jiffies)); \
> succeeded; \
> })
>
>
> is it just me, or do those arguments to time_before() look
> backwards?
with a quick grep, i found one other example that looks reversed.
from drivers/char/hvsi.c:
static void hvsi_drain_input(struct hvsi_struct *hp)
{
uint8_t buf[HVSI_MAX_READ] __ALIGNED__;
unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
while (time_before(end_jiffies, jiffies))
if (0 == hvsi_read(hp, buf, HVSI_MAX_READ))
break;
}
surely that's backwards as well, no?
rday
--
========================================================================
Robert P. J. Day Waterloo, Ontario, CANADA
Linux Consulting, Training and Kernel Pedantry.
Web page: http://crashcourse.ca
Twitter: http://twitter.com/rpjday
========================================================================
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: backwards busy wait using "time_before()"??
2009-12-31 16:40 backwards busy wait using "time_before()"?? Robert P. J. Day
2009-12-31 19:23 ` Robert P. J. Day
@ 2010-01-01 15:17 ` Andi Kleen
1 sibling, 0 replies; 3+ messages in thread
From: Andi Kleen @ 2010-01-01 15:17 UTC (permalink / raw)
To: Robert P. J. Day; +Cc: Linux Kernel Mailing List
"Robert P. J. Day" <rpjday@crashcourse.ca> writes:
> cpu_relax(); \
> } while (time_before(end_jiffies, jiffies)); \
> succeeded; \
> })
>
>
> is it just me, or do those arguments to time_before() look
> backwards?
Yes it looks backwards. The timeout path probably has been never
tested.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
^ permalink raw reply [flat|nested] 3+ messages in thread
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