diff mbox series

[net-next,2/6] net: ipa: reorder netdev pointer assignments

Message ID 20210804153626.1549001-3-elder@linaro.org (mailing list archive)
State Accepted
Delegated to: Netdev Maintainers
Headers show
Series net: ipa: more work toward runtime PM | expand

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Commit Message

Alex Elder Aug. 4, 2021, 3:36 p.m. UTC
Assign the ipa->modem_netdev and endpoint->netdev pointers *before*
registering the network device.  As soon as the device is
registered it can be opened, and by that time we'll want those
pointers valid.

Similarly, don't make those pointers NULL until *after* the modem
network device is unregistered in ipa_modem_stop().

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_modem.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

Comments

Jakub Kicinski Aug. 6, 2021, 1:27 a.m. UTC | #1
On Wed,  4 Aug 2021 10:36:22 -0500 Alex Elder wrote:
> Assign the ipa->modem_netdev and endpoint->netdev pointers *before*
> registering the network device.  As soon as the device is
> registered it can be opened, and by that time we'll want those
> pointers valid.
> 
> Similarly, don't make those pointers NULL until *after* the modem
> network device is unregistered in ipa_modem_stop().
> 
> Signed-off-by: Alex Elder <elder@linaro.org>

This one seems like a pretty legit race, net would be better if you
don't mind.
Jakub Kicinski Aug. 6, 2021, 1:41 a.m. UTC | #2
On Thu, 5 Aug 2021 18:27:12 -0700 Jakub Kicinski wrote:
> On Wed,  4 Aug 2021 10:36:22 -0500 Alex Elder wrote:
> > Assign the ipa->modem_netdev and endpoint->netdev pointers *before*
> > registering the network device.  As soon as the device is
> > registered it can be opened, and by that time we'll want those
> > pointers valid.
> > 
> > Similarly, don't make those pointers NULL until *after* the modem
> > network device is unregistered in ipa_modem_stop().
> > 
> > Signed-off-by: Alex Elder <elder@linaro.org>  
> 
> This one seems like a pretty legit race, net would be better if you
> don't mind.

Ah, this set was already applied, don't mind me :)
Alex Elder Aug. 6, 2021, 11:39 a.m. UTC | #3
On 8/5/21 8:27 PM, Jakub Kicinski wrote:
> On Wed,  4 Aug 2021 10:36:22 -0500 Alex Elder wrote:
>> Assign the ipa->modem_netdev and endpoint->netdev pointers *before*
>> registering the network device.  As soon as the device is
>> registered it can be opened, and by that time we'll want those
>> pointers valid.
>>
>> Similarly, don't make those pointers NULL until *after* the modem
>> network device is unregistered in ipa_modem_stop().
>>
>> Signed-off-by: Alex Elder <elder@linaro.org>
> 
> This one seems like a pretty legit race, net would be better if you
> don't mind.

I don't mind at all.  But now that it's accepted, I'm not sure how
to go about getting it back-ported.  Mainly I don't want to interfere
with any interaction between net/master and net-next/master...  Maybe
you're in a better position to do that.  And if so:

Fixes: 57f63faf0562 ("net: ipa: only set endpoint netdev pointer when in 
use")

I'll happily do it if you can tell me the best way how.  Thanks.

					-Alex
Alex Elder Aug. 6, 2021, 11:39 a.m. UTC | #4
On 8/5/21 8:41 PM, Jakub Kicinski wrote:
> On Thu, 5 Aug 2021 18:27:12 -0700 Jakub Kicinski wrote:
>> On Wed,  4 Aug 2021 10:36:22 -0500 Alex Elder wrote:
>>> Assign the ipa->modem_netdev and endpoint->netdev pointers *before*
>>> registering the network device.  As soon as the device is
>>> registered it can be opened, and by that time we'll want those
>>> pointers valid.
>>>
>>> Similarly, don't make those pointers NULL until *after* the modem
>>> network device is unregistered in ipa_modem_stop().
>>>
>>> Signed-off-by: Alex Elder <elder@linaro.org>
>>
>> This one seems like a pretty legit race, net would be better if you
>> don't mind.
> 
> Ah, this set was already applied, don't mind me :)

I really appreciate your review and feedback.  Applied or not,
it's valuable to me.

					-Alex
diff mbox series

Patch

diff --git a/drivers/net/ipa/ipa_modem.c b/drivers/net/ipa/ipa_modem.c
index 663a610979e70..ad4019e8016ec 100644
--- a/drivers/net/ipa/ipa_modem.c
+++ b/drivers/net/ipa/ipa_modem.c
@@ -231,13 +231,15 @@  int ipa_modem_start(struct ipa *ipa)
 	SET_NETDEV_DEV(netdev, &ipa->pdev->dev);
 	priv = netdev_priv(netdev);
 	priv->ipa = ipa;
+	ipa->name_map[IPA_ENDPOINT_AP_MODEM_TX]->netdev = netdev;
+	ipa->name_map[IPA_ENDPOINT_AP_MODEM_RX]->netdev = netdev;
+	ipa->modem_netdev = netdev;
 
 	ret = register_netdev(netdev);
-	if (!ret) {
-		ipa->modem_netdev = netdev;
-		ipa->name_map[IPA_ENDPOINT_AP_MODEM_TX]->netdev = netdev;
-		ipa->name_map[IPA_ENDPOINT_AP_MODEM_RX]->netdev = netdev;
-	} else {
+	if (ret) {
+		ipa->modem_netdev = NULL;
+		ipa->name_map[IPA_ENDPOINT_AP_MODEM_RX]->netdev = NULL;
+		ipa->name_map[IPA_ENDPOINT_AP_MODEM_TX]->netdev = NULL;
 		free_netdev(netdev);
 	}
 
@@ -276,10 +278,10 @@  int ipa_modem_stop(struct ipa *ipa)
 		/* If it was opened, stop it first */
 		if (netdev->flags & IFF_UP)
 			(void)ipa_stop(netdev);
-		ipa->name_map[IPA_ENDPOINT_AP_MODEM_RX]->netdev = NULL;
-		ipa->name_map[IPA_ENDPOINT_AP_MODEM_TX]->netdev = NULL;
-		ipa->modem_netdev = NULL;
 		unregister_netdev(netdev);
+		ipa->modem_netdev = NULL;
+		ipa->name_map[IPA_ENDPOINT_AP_MODEM_RX]->netdev = NULL;
+		ipa->name_map[IPA_ENDPOINT_AP_MODEM_TX]->netdev = NULL;
 		free_netdev(netdev);
 	}