Le mercredi 22 juin 2011 à 11:55 +0100, Russell King - ARM Linux a
écrit :
> From: Russell King <rmk+ker...@arm.linux.org.uk>
>
> Secondary CPU bringup typically calls calibrate_delay() during its
> initialization. However, calibrate_delay() modifies a global variable
> (loops_per_jiffy) used for udelay() and __delay().
>
> A side effect of 71c696b1 (calibrate: extract fall-back calculation
> into own helper) introduced in the 2.6.39 merge window means that we
> end up with a substantial period where loops_per_jiffy is zero. This
> causes the spinlock debugging code to malfunction:
...
>
> + loops_per_jiffy = lpj;
> printed = true;
> }
To be 100% safe, I would use
ACCESS_ONCE(loops_per_jiffy) = lpj;
But I assume no current gcc would be that stupid ;)
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