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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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