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    SubjectRe: [patch 2/13] signal/timer/event fds v6 - signalfd core ...
    On Mon, 19 Mar 2007, Eric W. Biederman wrote:

    > Davide Libenzi <davidel@xmailserver.org> writes:
    >
    > > struct signalfd_siginfo {
    > > __u32 signo; /* si_signo */
    > > __s32 err; /* si_errno */
    > > __s32 code; /* si_code */
    > > __u32 pid; /* si_pid */
    > > __u32 uid; /* si_uid */
    > > __s32 fd; /* si_fd */
    > > __u32 tid; /* si_fd */
    > > __u32 band; /* si_band */
    > > __u32 overrun; /* si_overrun */
    > > __u32 trapno; /* si_trapno */
    > > __s32 status; /* si_status */
    > > __s32 svint; /* si_int */
    > > __u64 svptr; /* si_ptr */
    > > __u64 utime; /* si_utime */
    > > __u64 stime; /* si_stime */
    > > __u64 addr; /* si_addr */
    > > };
    >
    > Shouldn't we pad this to 128 bytes like we do siginfo in case there are
    > more fields we need to include, or we need to extend the size of some
    > field?

    Yes, I guess we can.



    > I'm tempted to suggest we have a per arch function that tests current
    > to see if we are in a compat process or not so we can just use
    > siginfo. But that is probably overkill.
    >
    > > +
    > > +
    > > +struct signalfd_ctx {
    > > + struct list_head lnk;
    > > + wait_queue_head_t wqh;
    > > + sigset_t sigmask;
    > > + struct task_struct *tsk;
    > > +};
    >
    > I think you want to use a struct pid *pid instead of a pointer to the
    > task struct here. It is slightly less efficient (one more
    > dereference) but it means that we won't pin the task struct in memory
    > indefinitely. Pinning the task_struct like this makes for a very
    > interesting way to get around the limits on the number of processes a
    > user can have.

    Hmm, when the task is detached from the sighand, we get a notify, so I
    could do a put from there. This would avoid the extra de-reference. I need
    to verify locking though ...



    - Davide


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