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    SubjectRe: [PATCH 1/3] introduce PF_KTHREAD flag
    Date
    On Tuesday, 24 of June 2008, Oleg Nesterov wrote:
    > On 06/23, Andrew Morton wrote:
    > >
    > > On Mon, 23 Jun 2008 13:47:06 -0700
    > > Andrew Morton <akpm@linux-foundation.org> wrote:
    > >
    > > > I don't yet know how much additional damage will happen as a result.
    > >
    > > Lots.
    > >
    > > I restored the patches and just dropped the hunk:
    > >
    > > static int has_mm(struct task_struct *p)
    > > {
    > > - return (p->mm && !(p->flags & PF_BORROWED_MM));
    > > }
    > >
    > > /**
    > > --- 86,92 ----
    > >
    > > static int has_mm(struct task_struct *p)
    > > {
    > > + return (p->mm && !(p->flags & PF_KTHREAD));
    > > }
    > >
    > > due to that function having been turned into:
    > >
    > > static inline bool should_send_signal(struct task_struct *p)
    > > {
    > > return !(p->flags & PF_FREEZER_NOSIG);
    > > }
    > >
    > > Please check the result?
    >
    > Thanks, this looks OK.
    >
    > Rafael, can't freezer just use PF_KTHREAD (which btw kills PF_BORROWED_MM)
    > instead of the new PF_FREEZER_NOSIG flag? They look very similar, please
    > look at
    >
    > "[PATCH 1/3] introduce PF_KTHREAD flag"
    > http://marc.info/?l=linux-kernel&m=121233423530812
    >
    > "[PATCH 2/3] kill PF_BORROWED_MM in favour of PF_KTHREAD"
    > http://marc.info/?l=linux-kernel&m=121233423530820

    The problem is that some kernel threads may actually want to clear
    PF_FREEZER_NOSIG, but it would be invalid to clear PF_KTHREAD I think.

    Hmm, well, in principle we could use two flags for that, with the combinations
    of bits defined as follows:
    11 - user space task (freezable with a fake signal)
    10 - kernel thread freezable with a fake signal
    01 - kernel thread freezable withoug a fake signal
    00 - non-freezable kernel thread

    Thanks,
    Rafael


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