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    SubjectRe: [linux-pm] Is it supposed to be ok to call del_gendisk while userspace is frozen?
    Date
    On Saturday 15 May 2010, Nigel Cunningham wrote:
    > Hi.
    >
    > On 15/05/10 12:37, Alan Stern wrote:
    > > On Fri, 14 May 2010, Nigel Cunningham wrote:
    > >
    > >> Hi.
    > >
    > >>> Subject: [PATCH] fs: prevent hang on suspend/resume when MMC/SD card present
    > >>>
    > >>> Devices can come and go bus during suspend or resume, when the
    > >>> writeback thread is frozen, resulting in a hang. Prevent the hang
    > >>> by thawing the writeback thread in del_gendisk().
    > >
    > >> Why not just make it unfreezeable to start with?
    > >
    > > If the writeback thread were unfreezable, it might wake up and try to
    > > write dirty pages back to disks after they were already suspended.
    > > That would not lead to good consequences...
    >
    > If it syncs data as it should when we freeze processes, there won't be
    > any problem. Perhaps this is just an argument against making syncing
    > optional?

    No, there is a problem. The writeback threads were made freezable after some
    people had reported hangs during suspend that had been tracked down to that
    issue. IIRC.

    Rafael



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