netdev - Re: [PATCH net-next v4 1/5] netdevsim: maintain a list of probed netdevsims

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Message-ID: <ZYKsZdjn-ZOp11L4@nanopsycho>
Date: Wed, 20 Dec 2023 09:57:09 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: David Wei <dw@...idwei.uk>
Cc: Jakub Kicinski <kuba@...nel.org>, Sabrina Dubroca <sd@...asysnail.net>,
	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next v4 1/5] netdevsim: maintain a list of probed
 netdevsims

Wed, Dec 20, 2023 at 02:47:43AM CET, dw@...idwei.uk wrote:
>This patch adds a linked list nsim_dev_list of probed netdevsims, added
>during nsim_drv_probe() and removed during nsim_drv_remove(). A mutex
>nsim_dev_list_lock protects the list.

In the commit message, you should use imperative mood, command
the codebase what to do:
https://www.kernel.org/doc/html/v6.6/process/submitting-patches.html#describe-your-changes


>
>Signed-off-by: David Wei <dw@...idwei.uk>
>---
> drivers/net/netdevsim/dev.c       | 17 +++++++++++++++++
> drivers/net/netdevsim/netdevsim.h |  1 +
> 2 files changed, 18 insertions(+)
>
>diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
>index b4d3b9cde8bd..e30a12130e07 100644
>--- a/drivers/net/netdevsim/dev.c
>+++ b/drivers/net/netdevsim/dev.c
>@@ -35,6 +35,9 @@
> 
> #include "netdevsim.h"
> 
>+static LIST_HEAD(nsim_dev_list);
>+static DEFINE_MUTEX(nsim_dev_list_lock);
>+
> static unsigned int
> nsim_dev_port_index(enum nsim_dev_port_type type, unsigned int port_index)
> {
>@@ -1531,6 +1534,7 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
> 				 nsim_bus_dev->initial_net, &nsim_bus_dev->dev);
> 	if (!devlink)
> 		return -ENOMEM;
>+	mutex_lock(&nsim_dev_list_lock);

I don't follow. You claim you use this mutex to protect the list.
a) why don't you use spin-lock?
b) why don't don't you take the lock just for list manipulation?


> 	devl_lock(devlink);
> 	nsim_dev = devlink_priv(devlink);
> 	nsim_dev->nsim_bus_dev = nsim_bus_dev;
>@@ -1544,6 +1548,7 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
> 	spin_lock_init(&nsim_dev->fa_cookie_lock);
> 
> 	dev_set_drvdata(&nsim_bus_dev->dev, nsim_dev);
>+	list_add(&nsim_dev->list, &nsim_dev_list);
> 
> 	nsim_dev->vfconfigs = kcalloc(nsim_bus_dev->max_vfs,
> 				      sizeof(struct nsim_vf_config),
>@@ -1607,6 +1612,7 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
> 
> 	nsim_dev->esw_mode = DEVLINK_ESWITCH_MODE_LEGACY;
> 	devl_unlock(devlink);
>+	mutex_unlock(&nsim_dev_list_lock);
> 	return 0;
> 
> err_hwstats_exit:
>@@ -1668,8 +1674,18 @@ void nsim_drv_remove(struct nsim_bus_dev *nsim_bus_dev)
> {
> 	struct nsim_dev *nsim_dev = dev_get_drvdata(&nsim_bus_dev->dev);
> 	struct devlink *devlink = priv_to_devlink(nsim_dev);
>+	struct nsim_dev *pos, *tmp;
> 
>+	mutex_lock(&nsim_dev_list_lock);
> 	devl_lock(devlink);
>+
>+	list_for_each_entry_safe(pos, tmp, &nsim_dev_list, list) {
>+		if (pos == nsim_dev) {
>+			list_del(&nsim_dev->list);
>+			break;
>+		}
>+	}
>+
> 	nsim_dev_reload_destroy(nsim_dev);
> 
> 	nsim_bpf_dev_exit(nsim_dev);
>@@ -1681,6 +1697,7 @@ void nsim_drv_remove(struct nsim_bus_dev *nsim_bus_dev)
> 	kfree(nsim_dev->vfconfigs);
> 	kfree(nsim_dev->fa_cookie);
> 	devl_unlock(devlink);
>+	mutex_unlock(&nsim_dev_list_lock);
> 	devlink_free(devlink);
> 	dev_set_drvdata(&nsim_bus_dev->dev, NULL);
> }
>diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
>index 028c825b86db..babb61d7790b 100644
>--- a/drivers/net/netdevsim/netdevsim.h
>+++ b/drivers/net/netdevsim/netdevsim.h
>@@ -277,6 +277,7 @@ struct nsim_vf_config {
> 
> struct nsim_dev {
> 	struct nsim_bus_dev *nsim_bus_dev;
>+	struct list_head list;
> 	struct nsim_fib_data *fib_data;
> 	struct nsim_trap_data *trap_data;
> 	struct dentry *ddir;
>-- 
>2.39.3
>