On Mon, 9 Jul 2007, Pavel Machek wrote:
Actaully, I'm perfectly fine with that, as long as each task blocked by the
driver due to suspend has PF_FROZEN (or something similar) set. Then, at
least theoretically, we'll be able to drop the freezer from the suspend code
path and move it after device_suspend() (or the hibernation-specific
equivalent) for hibernation (in that case there shouldn't be a problem with
any task waiting on I/O while the freezer is running ;-)).
I don't see the need for a freezer for snapshot but that's a different
issue. (stop_machine looks good enough to me).
Freezer is not needed for snapshot -- it is needed so that we can
write out the snapshot to disk without the need for special
drivers/block/simple-ide-for-suspend.c. (We are doing snapshot, then
write to disk from userland code in uswsusp).
instead of trying to freeze most of the system, could you do something
like start a virtual machine sandbox to write the data out, and not let
any userspace other then the sandbox operate?
you would need to throw away disk buffers so that you don't mix current
pending I/O with I/O from the sandbox, and this would be a visable change
for how suspend is setup, but wouldn't this work?
David Lang
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