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    SubjectRe: [RFC][PATCH -mm 3/3] PM: Disable _request_firmware before hibernation/suspend
    On Sun, May 27, 2007 at 11:45:03PM +0200, Rafael J. Wysocki wrote:
    > On Sunday, 27 May 2007 22:49, Matthew Garrett wrote:
    > > If we remove process freezing in STR, this should just work[1] without the
    > > need to complicate things.
    >
    > Under the (optimistic, IMO) assumption that the relevant user space task won't
    > block on I/O with a suspended device involved or something like this.

    Yeah, I forgot the footnote that was going to mention that. Clearly
    there are issues if this is on some block device that hasn't been
    resumed yet.

    > BTW, I know of two subsystems that want their kernel threads to be frozen for
    > synchronization purposes. Please see these messages:
    >
    > 1) https://lists.linux-foundation.org/pipermail/linux-pm/2007-May/012592.html
    > (plus follow up)
    >
    > 2) http://marc.info/?l=linux-kernel&m=117919066830575&w=2

    I'm not entirely sold on this. The issue is that there's the possibility
    of races during suspend/resume? It sounds like that should be
    implemented in the driver, rather than depending on a side-effect of
    process freezing. Otherwise there's no way of selectively suspending
    that device.

    > Besides, there's the hibernation that needs to freeze tasks for another reason,
    > so it needs some way to ensure that drivers won't request firmware while
    > the user land is frozen.

    I agree that that's an issue right now, but I think we should see if
    this is repairable without just breaking those drivers. One option would
    be to defer resuming them until userspace is alive again - that would be
    no worse than the suspend to RAM case without process freezing.

    --
    Matthew Garrett | mjg59@srcf.ucam.org
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