Re: [patch 2/13] signal/timer/event fds v6 - signalfd core ...

[Davide Libenzi]

On Mon, 19 Mar 2007, Eric W. Biederman wrote:

> Davide Libenzi <davidel@xxxxxxxxxxxxxxx> 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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