linux-kernel - Re: clocksource mutex deadlock, cat current

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Message-ID: <20100208194734.GA20316@rhlx01.hs-esslingen.de>
Date:	Mon, 8 Feb 2010 20:47:34 +0100
From:	Andreas Mohr <andi@...as.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andreas Mohr <andi@...as.de>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	John Stultz <johnstul@...ibm.com>
Subject: Re: clocksource mutex deadlock, cat current_clocksource
	(2.6.33-rc6/7)

Hi,

On Mon, Feb 08, 2010 at 11:06:58AM +0100, Thomas Gleixner wrote:
> EIP: 0060:[<c1045170>] EFLAGS: 00000082 CPU: 0
> EIP is at timekeeping_forward_now+0x116/0x139
> 
> I don't see what might make the machine stuck here. Can you decode the
> source line with "addr2line -e vmlinux c1045170" please ?

And the winner is:
/usr/src/linux-2.6.33-rc7/include/linux/math64.h:91

static __always_inline u32
__iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
{
        u32 ret = 0;

        while (dividend >= divisor) {
                /* The following asm() prevents the compiler from
                   optimising this loop into a modulo operation.  */
                asm("" : "+rm"(dividend));

                dividend -= divisor;
                ret++;
        }

        *remainder = dividend;

        return ret;
}


while ......



Do I see a divisor == 0 here?? ;)

Andreas Mohr
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