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    SubjectRe: [Linux-fbdev-devel] [2.6.29-rc2] fb_mmap: circular locking dependency on hibernation
    On 2009-01-31 18:44, Geert Uytterhoeven wrote:
    > On Sat, 31 Jan 2009, Andrea Righi wrote:
    >> On 2009-01-30 05:15, Andrey Borzenkov wrote:
    >>> On 29 of January 2009 12:10:11 Geert Uytterhoeven wrote:
    >>>> On Tue, 27 Jan 2009, Andrey Borzenkov wrote:
    >> fbcon: avoid circular locking dependency between fb_info->lock and mm->mmap_sem
    >> In fbcon notifier the handler for FB_EVENT_SET_CONSOLE_MAP doesn't need
    >> to hold fb_info->lock.
    >> Simply unlock it before calling set_con2fb_map(), that could try to
    >> acquire mm->mmap_sem to avoid a circular locking dependency with
    >> fb_mmap() (that acquires mm->mmap_sem -> fb_info-lock).
    > However, set_con2fb_map() accesses the array of fb_info pointers
    > registered_fb[], which seems to be a bit unsafe now the BKL is no longer held.

    mmmh.. not sure about that, registered_fb[] was never accessed with
    fb_info->lock held, see register/unregister_framebuffer().

    But maybe this is another issue, and anyway, the array and also
    num_registered_fb don't seem to be protected at all...


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      Last update: 2009-01-31 19:15    [W:0.037 / U:6.540 seconds]
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