Re: radeon_pm.c locking problem

[Kronos <kronos@people.it>]

Il Fri, Jul 02, 2004 at 01:29:38PM -0400, John Zielinski ha scritto: 
> *This message was transferred with a trial version of CommuniGate(tm) Pro*
> There's a post in the lkml from a Stanford researcher working on a tool 
> to sniff out locking problems.  In his post he gave an example from the 
> radeon_pm.c file.  Just want to make sure the appropriate people noticed 
> the post.  It's subject is "[BUGS] [CHECKER] 99 synchronization bugs and 
> a lock summary database".

Hum, it seems a real bug because OUTPLL is a macro. The following line
(radeon_pm.c:323, but there are more of them):

OUTPLL(pllPIXCLKS_CNTL, INPLL(pllPIXCLKS_CNTL) & ~PIXCLKS_CNTL__PIX2CLK_SRC_SEL_MASK);

is expanded in:

do {
        unsigned long flags;
        spin_lock_irqsave(&rinfo->reg_lock, flags);
        __OUTPLL(pllPIXCLKS_CNTL, INPLL(pllPIXCLKS_CNTL) & ~PIXCLKS_CNTL__PIX2CLK_SRC_SEL_MASK);
        spin_unlock_irqrestore(&rinfo->reg_lock, flags);
} while(0)

and INPLL will try to reacquire the lock ->reg_lock. We could either use
__INPLL (which does not take the lock) or make OUTPLL an inline function
(in this way INPLL is called before entering the function).

Ben?

Luca
-- 
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