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Message-ID: <806d2df6-68d3-4319-8ce6-7049563508cf@tuxon.dev>
Date: Thu, 23 Jan 2025 13:33:30 +0200
From: Claudiu Beznea <claudiu.beznea@...on.dev>
To: Kory Maincent <kory.maincent@...tlin.com>,
Paul Barker <paul.barker.ct@...renesas.com>,
Niklas Söderlund <niklas.soderlund@...natech.se>,
Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Mikhail Ulyanov <mikhail.ulyanov@...entembedded.com>,
Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
Niklas Söderlund <niklas.soderlund+renesas@...natech.se>,
Claudiu Beznea <claudiu.beznea.uj@...renesas.com>, netdev@...r.kernel.org,
linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: ravb: Fix missing rtnl lock in suspend path
Hi, Kory,
On 22.01.2025 18:19, Kory Maincent wrote:
> Fix the suspend path by ensuring the rtnl lock is held where required.
> Calls to ravb_open, ravb_close and wol operations must be performed under
> the rtnl lock to prevent conflicts with ongoing ndo operations.
>
> Without this fix, the following warning is triggered:
> [ 39.032969] =============================
> [ 39.032983] WARNING: suspicious RCU usage
> [ 39.033019] -----------------------------
> [ 39.033033] drivers/net/phy/phy_device.c:2004 suspicious
> rcu_dereference_protected() usage!
> ...
> [ 39.033597] stack backtrace:
> [ 39.033613] CPU: 0 UID: 0 PID: 174 Comm: python3 Not tainted
> 6.13.0-rc7-next-20250116-arm64-renesas-00002-g35245dfdc62c #7
> [ 39.033623] Hardware name: Renesas SMARC EVK version 2 based on
> r9a08g045s33 (DT)
> [ 39.033628] Call trace:
> [ 39.033633] show_stack+0x14/0x1c (C)
> [ 39.033652] dump_stack_lvl+0xb4/0xc4
> [ 39.033664] dump_stack+0x14/0x1c
> [ 39.033671] lockdep_rcu_suspicious+0x16c/0x22c
> [ 39.033682] phy_detach+0x160/0x190
> [ 39.033694] phy_disconnect+0x40/0x54
> [ 39.033703] ravb_close+0x6c/0x1cc
> [ 39.033714] ravb_suspend+0x48/0x120
> [ 39.033721] dpm_run_callback+0x4c/0x14c
> [ 39.033731] device_suspend+0x11c/0x4dc
> [ 39.033740] dpm_suspend+0xdc/0x214
> [ 39.033748] dpm_suspend_start+0x48/0x60
> [ 39.033758] suspend_devices_and_enter+0x124/0x574
> [ 39.033769] pm_suspend+0x1ac/0x274
> [ 39.033778] state_store+0x88/0x124
> [ 39.033788] kobj_attr_store+0x14/0x24
> [ 39.033798] sysfs_kf_write+0x48/0x6c
> [ 39.033808] kernfs_fop_write_iter+0x118/0x1a8
> [ 39.033817] vfs_write+0x27c/0x378
> [ 39.033825] ksys_write+0x64/0xf4
> [ 39.033833] __arm64_sys_write+0x18/0x20
> [ 39.033841] invoke_syscall+0x44/0x104
> [ 39.033852] el0_svc_common.constprop.0+0xb4/0xd4
> [ 39.033862] do_el0_svc+0x18/0x20
> [ 39.033870] el0_svc+0x3c/0xf0
> [ 39.033880] el0t_64_sync_handler+0xc0/0xc4
> [ 39.033888] el0t_64_sync+0x154/0x158
> [ 39.041274] ravb 11c30000.ethernet eth0: Link is Down
>
> Reported-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> Closes: https://lore.kernel.org/netdev/4c6419d8-c06b-495c-b987-d66c2e1ff848@tuxon.dev/
> Fixes: 0184165b2f42 ("ravb: add sleep PM suspend/resume support")
> Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
I've test it. Looks good.
Thank you for your patch. However, I think this could be simplified. The
locking scheme looks complicated to me. E.g., this one works too:
diff --git a/drivers/net/ethernet/renesas/ravb_main.c
b/drivers/net/ethernet/renesas/ravb_main.c
index bc395294a32d..cfe4f0f364f3 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -3217,10 +3217,16 @@ static int ravb_suspend(struct device *dev)
netif_device_detach(ndev);
- if (priv->wol_enabled)
- return ravb_wol_setup(ndev);
+ if (priv->wol_enabled) {
+ rtnl_lock();
+ ret = ravb_wol_setup(ndev);
+ rtnl_unlock();
+ return ret;
+ }
+ rtnl_lock();
ret = ravb_close(ndev);
+ rtnl_unlock();
if (ret)
return ret;
@@ -3247,7 +3253,9 @@ static int ravb_resume(struct device *dev)
/* If WoL is enabled restore the interface. */
if (priv->wol_enabled) {
+ rtnl_lock();
ret = ravb_wol_restore(ndev);
+ rtnl_unlock();
if (ret)
return ret;
} else {
@@ -3257,7 +3265,9 @@ static int ravb_resume(struct device *dev)
}
/* Reopening the interface will restore the device to the working
state. */
+ rtnl_lock();
ret = ravb_open(ndev);
+ rtnl_unlock();
if (ret < 0)
goto out_rpm_put;
> ---
> drivers/net/ethernet/renesas/ravb_main.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index bc395294a32d..2c6d8e4966c3 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -3217,10 +3217,15 @@ static int ravb_suspend(struct device *dev)
>
> netif_device_detach(ndev);
>
> - if (priv->wol_enabled)
> - return ravb_wol_setup(ndev);
> + rtnl_lock();
> + if (priv->wol_enabled) {
> + ret = ravb_wol_setup(ndev);
> + rtnl_unlock();
> + return ret;
> + }
>
> ret = ravb_close(ndev);
> + rtnl_unlock();
> if (ret)
> return ret;
>
> @@ -3245,19 +3250,25 @@ static int ravb_resume(struct device *dev)
> if (!netif_running(ndev))
> return 0;
>
> + rtnl_lock();
> /* If WoL is enabled restore the interface. */
> if (priv->wol_enabled) {
> ret = ravb_wol_restore(ndev);
> - if (ret)
> + if (ret) {
> + rtnl_unlock();
> return ret;
> + }
> } else {
> ret = pm_runtime_force_resume(dev);
> - if (ret)
> + if (ret) {
> + rtnl_unlock();
> return ret;
> + }
> }
>
> /* Reopening the interface will restore the device to the working state. */
> ret = ravb_open(ndev);
> + rtnl_unlock();
> if (ret < 0)
> goto out_rpm_put;
>
>
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