netdev - Re: [PATCH net] forcedeth: Fix an error handling path in nv

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Date: Mon, 22 May 2023 13:10:56 +0200
From: Simon Horman <simon.horman@...igine.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Rain River <rain.1986.08.12@...il.com>,
	Zhu Yanjun <zyjzyj2000@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Ayaz Abdulla <aabdulla@...dia.com>, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net] forcedeth: Fix an error handling path in nv_probe()

On Mon, May 22, 2023 at 01:35:38PM +0300, Dan Carpenter wrote:
> On Mon, May 22, 2023 at 12:12:48PM +0200, Simon Horman wrote:
> > On Sat, May 20, 2023 at 10:30:17AM +0200, Christophe JAILLET wrote:
> > > If an error occures after calling nv_mgmt_acquire_sema(), it should be
> > > undone with a corresponding nv_mgmt_release_sema() call.
> > 
> > nit: s/occures/occurs/
> > 
> > > 
> > > Add it in the error handling path of the probe as already done in the
> > > remove function.
> > 
> > I was going to ask what happens if nv_mgmt_acquire_sema() fails.
> > Then I realised that it always returns 0.
> > 
> > Perhaps it would be worth changing it's return type to void at some point.
> >
> 
> What? No?  It returns true on success and false on failure.
> 
> drivers/net/ethernet/nvidia/forcedeth.c
>   5377  static int nv_mgmt_acquire_sema(struct net_device *dev)
>   5378  {
>   5379          struct fe_priv *np = netdev_priv(dev);
>   5380          u8 __iomem *base = get_hwbase(dev);
>   5381          int i;
>   5382          u32 tx_ctrl, mgmt_sema;
>   5383  
>   5384          for (i = 0; i < 10; i++) {
>   5385                  mgmt_sema = readl(base + NvRegTransmitterControl) & NVREG_XMITCTL_MGMT_SEMA_MASK;
>   5386                  if (mgmt_sema == NVREG_XMITCTL_MGMT_SEMA_FREE)
>   5387                          break;
>   5388                  msleep(500);
>   5389          }
>   5390  
>   5391          if (mgmt_sema != NVREG_XMITCTL_MGMT_SEMA_FREE)
>   5392                  return 0;
>   5393  
>   5394          for (i = 0; i < 2; i++) {
>   5395                  tx_ctrl = readl(base + NvRegTransmitterControl);
>   5396                  tx_ctrl |= NVREG_XMITCTL_HOST_SEMA_ACQ;
>   5397                  writel(tx_ctrl, base + NvRegTransmitterControl);
>   5398  
>   5399                  /* verify that semaphore was acquired */
>   5400                  tx_ctrl = readl(base + NvRegTransmitterControl);
>   5401                  if (((tx_ctrl & NVREG_XMITCTL_HOST_SEMA_MASK) == NVREG_XMITCTL_HOST_SEMA_ACQ) &&
>   5402                      ((tx_ctrl & NVREG_XMITCTL_MGMT_SEMA_MASK) == NVREG_XMITCTL_MGMT_SEMA_FREE)) {
>   5403                          np->mgmt_sema = 1;
>   5404                          return 1;
>                                 ^^^^^^^^^
> Success path.
> 
>   5405                  } else
>   5406                          udelay(50);
>   5407          }
>   5408  
>   5409          return 0;
>   5410  }

Thanks Dan,

my eyes deceived me.

In that case, my question is: what if nv_mgmt_acquire_sema() fails?
But I think the answer is that nv_mgmt_release_sema() will do
nothing because mgmt_sema is not set.

So I think we are good.