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

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Message-ID: <8dbb4087-db01-fbbf-4e96-a5b0e170249a@wanadoo.fr>
Date:   Mon, 22 May 2023 19:13:43 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Simon Horman <simon.horman@...igine.com>,
        Dan Carpenter <dan.carpenter@...aro.org>
Cc:     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()

Le 22/05/2023 à 13:10, Simon Horman a écrit :
> 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.

At least, it is my understanding.

Can you fix the typo s/occures/occurs/ when applying the patch, or do 
you really need a v2 only for that?

CJ.

> 
> So I think we are good.
> 
> 
>