[PATCHv5 02/10] ARM: OMAP3+: voltage: add support for voltagedomain usecounts
From: Russell King - ARM Linux <hidden>
Date: 2012-09-25 09:41:00
Also in:
linux-omap
On Tue, Sep 25, 2012 at 12:32:37PM +0300, Tero Kristo wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c index ba49029..ca54aec 100644 --- a/arch/arm/mach-omap2/powerdomain.c +++ b/arch/arm/mach-omap2/powerdomain.c@@ -1475,10 +1477,16 @@ int pwrdm_state_switch(struct powerdomain *pwrdm) */ void pwrdm_clkdm_enable(struct powerdomain *pwrdm) { + unsigned long flags; + if (!pwrdm) return; - atomic_inc(&pwrdm->usecount); + if (atomic_inc_return(&pwrdm->usecount) == 1) { + spin_lock_irqsave(&pwrdm->lock, flags); + voltdm_pwrdm_enable(pwrdm->voltdm.ptr); + spin_unlock_irqrestore(&pwrdm->lock, flags); + }
This looks like the classic "I like atomic types because they have magic properties" brain-deadness. What would happen to users of this if you had this sequence: pwrdm->usecount starts off as 1. Thread0 Thread1 atomic_inc_return() (returns 1) atomic_inc_return() (returns 2) starts using stuff in power domain spin_lock_irqsave() voltdm_pwrdm_enable() spin_unlock_irqrestore() ?