Re: [PATCH] net: Convert net_mutex into rw_semaphore and down read it on net->init/->exit

[Eric Dumazet]

On Tue, 2017-11-14 at 16:53 +0300, Kirill Tkhai wrote:
> Curently mutex is used to protect pernet operations list. It makes
> cleanup_net() to execute ->exit methods of the same operations set,
> which was used on the time of ->init, even after net namespace is
> unlinked from net_namespace_list.
> 
...

> The solution is to convert net_mutex to the rw_semaphore. Then,
> pernet_operations::init/::exit methods, modifying the net-related data,
> will require down_read() locking only, while down_write() will be used
> for changing pernet_list.
> 
...

> This patch requires commit 76f8507f7a64 "locking/rwsem: Add down_read_killable()"
> from Linus tree (not in net-next yet).


Looks great, thanks for doing this.

I wonder if the down_read_killable() is really needed, maybe a
down_read() would not be blocking the thread too long after this change.