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SubjectRe: [PATCH] nbd: Move socket shutdown out of spinlock
From
Hi Markus,


On Thu, May 12, 2016 at 3:13 PM, Markus Pargmann <mpa@pengutronix.de> wrote:
> spinlocked ranges should be small and not contain calls into huge
> subfunctions. Fix my mistake and just get the pointer to the socket
> instead of doing everything with spinlock held.
>
> Reported-by: Mikulas Patocka <mikulas@twibright.com>
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
> ---
> drivers/block/nbd.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 0b892eed06a0..157bf3da876e 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -173,20 +173,22 @@ static void nbd_end_request(struct nbd_device *nbd, struct request *req)
> */
> static void sock_shutdown(struct nbd_device *nbd)
> {
> + struct socket *sock;
> +
> spin_lock_irq(&nbd->sock_lock);
> + sock = nbd->sock;
> + nbd->sock = NULL;
> + spin_unlock_irq(&nbd->sock_lock);
>
> - if (!nbd->sock) {
> - spin_unlock_irq(&nbd->sock_lock);
> + if (!sock)
> return;
> - }
> +
> + del_timer(&nbd->timeout_timer);
>
> dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
> - kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
> - sockfd_put(nbd->sock);
> - nbd->sock = NULL;
> - spin_unlock_irq(&nbd->sock_lock);
> + kernel_sock_shutdown(sock, SHUT_RDWR);
> + sockfd_put(sock);
>
> - del_timer(&nbd->timeout_timer);
> }
>
> static void nbd_xmit_timeout(unsigned long arg)

I was concerned about nbd_xmit_timeout as well. There's also a call to
kernel_sock_shutdown,
while holding the spin_lock in the timeout. The above is ok for
sock_shutdown but some kind of change
is also required in nbd_xmit_timeout as well. My patch addressed both these.

Can you have a look at that again.


> --
> 2.8.0.rc3
>



--
---P.K.S

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