[PATCH net-next] can: grcan: move napi_enable() from under spin lock

[PATCH net-next] can: grcan: move napi_enable() from under spin lock

[Jakub Kicinski]

I don't see any reason why napi_enable() needs to be under the lock,
only reason I could think of is if the IRQ also took this lock
but it doesn't. napi_enable() will soon need to sleep.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
Marc, if this is correct is it okay for me to take via net-next
directly? I have a bunch of patches which depend on it.

CC: mkl@pengutronix.de
CC: mailhol.vincent@wanadoo.fr
CC: linux-can@vger.kernel.org
---
 drivers/net/can/grcan.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
index cdf0ec9fa7f3..21a61b86f67d 100644
--- a/drivers/net/can/grcan.c
+++ b/drivers/net/can/grcan.c
@@ -1073,9 +1073,10 @@ static int grcan_open(struct net_device *dev)
 	if (err)
 		goto exit_close_candev;
 
+	napi_enable(&priv->napi);
+
 	spin_lock_irqsave(&priv->lock, flags);
 
-	napi_enable(&priv->napi);
 	grcan_start(dev);
 	if (!(priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))
 		netif_start_queue(dev);
-- 
2.47.1

Re: [PATCH net-next] can: grcan: move napi_enable() from under spin lock

[Vincent Mailhol]

On 11/01/2025 at 11:47, Jakub Kicinski wrote:
> I don't see any reason why napi_enable() needs to be under the lock,
> only reason I could think of is if the IRQ also took this lock
> but it doesn't. napi_enable() will soon need to sleep.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Acked-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

> ---
> Marc, if this is correct is it okay for me to take via net-next
> directly? I have a bunch of patches which depend on it.

Even if the question is not addressed to me, I am personally fine if
this directly goes into net-next.

> CC: mkl@pengutronix.de
> CC: mailhol.vincent@wanadoo.fr
> CC: linux-can@vger.kernel.org
> ---
>  drivers/net/can/grcan.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
> index cdf0ec9fa7f3..21a61b86f67d 100644
> --- a/drivers/net/can/grcan.c
> +++ b/drivers/net/can/grcan.c
> @@ -1073,9 +1073,10 @@ static int grcan_open(struct net_device *dev)
>  	if (err)
>  		goto exit_close_candev;
>  
> +	napi_enable(&priv->napi);
> +
>  	spin_lock_irqsave(&priv->lock, flags);
>  
> -	napi_enable(&priv->napi);
>  	grcan_start(dev);
>  	if (!(priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))
>  		netif_start_queue(dev);


Yours sincerely,
Vincent Mailhol

Re: [PATCH net-next] can: grcan: move napi_enable() from under spin lock

[Francois Romieu]

Jakub Kicinski <kuba@kernel.org> :
> I don't see any reason why napi_enable() needs to be under the lock,
> only reason I could think of is if the IRQ also took this lock
> but it doesn't. napi_enable() will soon need to sleep.

Anything that depends on the napi handler being run may also behave
differently because of 'priv->resetting = false;' and
'priv->closing = false;' also done under the lock after napi_enable in
the original version.

Both priv->closing and priv->resetting are always accessed with lock
held so it's fine.

(nothing to chew in grcan_start either)

Reviewed-by: Francois Romieu <romieu@fr.zoreil.com>

-- 
Ueimor

Re: [PATCH net-next] can: grcan: move napi_enable() from under spin lock

[Marc Kleine-Budde]

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On 10.01.2025 18:47:42, Jakub Kicinski wrote:
> I don't see any reason why napi_enable() needs to be under the lock,
> only reason I could think of is if the IRQ also took this lock
> but it doesn't. napi_enable() will soon need to sleep.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> Marc, if this is correct is it okay for me to take via net-next
> directly? I have a bunch of patches which depend on it.

Yes, please take it via net-next directly.

Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>

Marc

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Re: [PATCH net-next] can: grcan: move napi_enable() from under spin lock

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 10 Jan 2025 18:47:42 -0800 you wrote:
> I don't see any reason why napi_enable() needs to be under the lock,
> only reason I could think of is if the IRQ also took this lock
> but it doesn't. napi_enable() will soon need to sleep.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> Marc, if this is correct is it okay for me to take via net-next
> directly? I have a bunch of patches which depend on it.
> 
> [...]

Here is the summary with links:
  - [net-next] can: grcan: move napi_enable() from under spin lock
    https://git.kernel.org/netdev/net-next/c/7c125d5b767b

You are awesome, thank you!
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