Re: [PATCH] epoll bits 0.34

Re: [PATCH] epoll bits 0.34

[Manfred Spraul]

>
>
> - Cleaned up locking
>
The cleanup is dangerous/broken: You call f_op->poll with disabled 
interrupts.

> 	/* We have to drop the new item inside our item list to keep track of it */
> 	write_lock_irqsave(&ep->lock, flags);
> 
>+	/* Add the current item to the hash table */
> 	list_add(&dpi->llink, ep_hash_entry(ep, ep_hash_index(ep, tfile)));
> 
>+	/* Attach the item to the poll hooks and get current event bits */
>+	revents = tfile->f_op->poll(tfile, &pt);
>+
>  
>
Which file descriptors are pollable with eventpoll? For example rtc_poll 
does

    spin_lock_irq();
    do_work();
    spin_unlock_irq();

I'm sure that there are other drivers that are be affected, I haven't 
checked networking.

And is that really needed? Could you do the real work in the poll 
callback instead of locking around the f_op call?

--
    Manfred

Re: [PATCH] epoll bits 0.34

[Davide Libenzi]

On Mon, 11 Nov 2002, Manfred Spraul wrote:

> Which file descriptors are pollable with eventpoll? For example rtc_poll
> does
>
>     spin_lock_irq();
>     do_work();
>     spin_unlock_irq();
>
> I'm sure that there are other drivers that are be affected, I haven't
> checked networking.
>
> And is that really needed? Could you do the real work in the poll
> callback instead of locking around the f_op call?

I'll take care of it, thx for your precious input.



- Davide