linux-kernel - Question about C language.

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Message-ID: <38b2ab8a0803210846p2f9b92adr951fe7fa0444de63@mail.gmail.com>
Date:	Fri, 21 Mar 2008 16:46:09 +0100
From:	"Francis Moreau" <francis.moro@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Question about C language.

Hello,

I know it's a bit out of topic but this is something I need to clarify for
writing a Linux driver... hope you don't mind.

In my driver I have a global variable that controls a loop such as:

int my_condition;

void change_my_condition(int new)
{
    my_condition = new;
}

int foo(void)
{
    /* irqs are disabled */
    my_condition = 1;
    do {
        ....
        local_irq_enable();
        cpu_sleep();
        local_irq_disable();

   } while (my_condition);

}

This variable is modified by an interrupt handler define in another file
by using 'change_my_condition' function.

By reading the ISO C99 specification, I _think_ that I needn't any
kind of barrier
or even use the volatile type qualifier for my_condition variable to make a true
access to 'my_condition' in the controlling expression of the while, but I'm not
sure.

Coud anybody confirm ?

Thanks,
-- 
Francis
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