Re: [PATCH net-next v2] ppp: remove ppp->closing check

On 2/2/26 10:21 AM, Qingfang Deng wrote:
> The ppp->closing flag is used to test if an interface is closing down.
> However, when .ndo_uninit() is called (where ppp->closing is set to 1),
> dev_close() has already brought down the interface, and
> synchronize_net() guarantees that no pending TX/RX in the network path
> can take place. Thus, the check in the network path is unnecessary.
> 
> For file operations - ppp_read(), ppp_write(), and ppp_poll(), can
> normally still send or receive skbs. ppp_read() and ppp_poll() are safe
> because ppp_dev_uninit() sets pf->dead before waking them up, causing
> both to exit cleanly. 

Please report the accurate call sequence that would lead to such syscall
complete cleanly. Also what if ndo_uninit() happens just after the
user-space has been woken-up?

> ppp_write() does not check pf->dead, but
> ppp_push() verifies that ppp->channels list is not empty before sending.
> 
> Remove the ppp->closing check.

This still feel risky to me and it's not clear which would be the
goal/gain. It this change performance oriented? If so please included
actual figures.

Thanks,

Paolo