Re: suspend.c vs driver-model.txt

[Pavel Machek <pavel-AlSwsSmVLrQ@public.gmane.org>]

Hi!

> >Discussing with who?
> 
> We had a Power Management BOF there, among others, Patrick Mochel,
> Greg KH, Andy, Paulus, Jeff Garzik, ...

Oops... I guess I should have been there :-(. Sorry.

> >Its rather simple: free half of memory, stop everything, save device
> >state, copy used memory into free memory, continue devices, save data
> >from "free" memory into swap.
> 
> Ok, so you first push as much as you can to swap to free half
> of memory. Then, when you say you copy used memory, I assume you copy
> all of RAM including kernel memory (kernel data structures etc...)
> right ?

Yes.

> What do you mean by "stop everything" ? Stop user processes ? Kernel
> threads ? both ? 

Stop all user processes and all kernel processes that could cause
trouble. Don't stop kapm-idled (for example) but be sure to stop
ext3-commitd (or how is that beast called).

> Then, you only save device state (and then suspend
> devices) after you have "stopped everything" ?

Yes.

Code looks like this:

void do_software_suspend(void)
{
        arch_prepare_suspend();
        if (prepare_suspend_console())
                printk( "%sCan't allocate a console... proceeding\n", name_suspend);
        if (!prepare_suspend_processes()) {

                /* At this point, all user processes and "dangerous"
                   kernel threads are stopped. Free some memory, as we
                   need half of memory free. */

                free_some_memory();

                /* No need to invalidate any vfsmnt list -- they will be valid after resume, anyway.
                 *
                 * We sync here -- so you have consistent filesystem state when things go wrong.
                 * -- so that noone writes to disk after we do atomic copy of data.
                 */
                PRINTK("Syncing disks before copy\n");
                do_suspend_sync();

                /* Save state of all device drivers, and stop them. */
                if(drivers_suspend()==0)
                        /* If stopping device drivers worked, we proceed basically into
                         * suspend_save_image.
                         *
                         * do_magic(0) returns after system is resumed.
                         *
                         * do_magic() copies all "used" memory to "free" memory, then
                         * unsuspends all device drivers, and writes memory to disk
                         * using normal kernel mechanism.
                         */
                        do_magic(0);
                PRINTK("Restarting processes...\n");
                thaw_processes();
        }
        software_suspend_enabled = 1;
        MDELAY(1000);
        restore_console ();
}

(Most comments were added 5 minutes ago).

Does it look understendable now?
									Pavel
-- 
Worst form of spam? Adding advertisment signatures ala sourceforge.net.
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