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It looks like this is a general problem after ICS upgrade for Sony Xperia phone.
I didn't have this problem before even in worse firmware 6.1.1.B.1.10, but after using 6.1.1.B.1.54 two weeks, I have the problem now...
I can connect to AP after boot.
After use for a little time, the process "wpa_supplicant" start running, and never stop, just like the screenshot below (right-top corner).
When the process "wpa_supplicant" is running, I can neither turn off the WiFi, nor make any setting change about WiFi.
What I can do is reboot.
It looks that the WiFi status was been locked by this process.
According the information on the web (reference), this issue can be fixed after delete the file /data/misc/wifi/wpa_supplicant_bagscan.db. (rooted required)
But this file will automatic generated by wpa_supplicant, so the same problem may happens again.
Is there any way to fix this issue without rooted?
WHY SONY? YOU FORGOT ABOUT US?
FIX THE DEMN WIFI CRL!
YOU SHOULD BE ASHAMED SONY!!!
Submitted a support question to xperia care and the muppets sent the script response below. I said I couldn't turn off WiFi and they respond answering how to connect!!
Thank you for contacting the Sony Xperia support centre.
We are sorry to hear you are having problems connecting to Wi-Fi on your Sony Xperia U.
We would first suggest that you check the IP Address is correct as it may be your router is providing a false IP Address which is the reason you are unable to use the connection. Please follow the below steps to check this:
1. Open the Menu
2. Select Settings
3. Go in to Wi-Fi
4. Tap the SSID (network/router name) of your Network
5. Check the IP Address, If this begins 169 then this indicates that it is not connecting to the WLAN
If this is the case then this may indicate that the router has some form of client management system such as DHCP (Dynamic Host Control Protocol), used to manage many clients on one router. Or MAC (Media Access Control) address filtering, used to allow or block access based on the unique MAC address of your devices Wi-Fi chip. We would therefore suggest contacting the manufacturer of the router to amend such client access filters to permit access.
If the IP address is listed as 192.168.0.01 or 10.1.1.1 for example (not 169...) - Try connecting to a web page such as www.bbc.co.uk via the handsets web browser.
If this does connect then this indicates that your handset is functioning correctly. If your handset is customised with your network operator software version then this may indicate why you may not be able to connect to certain web pages. Your network operator may restrict access to certain sites in preference of the 3G, GPRS settings.
If this still does not connect, we would suggest that you try Google's DNS address by entering 64.233.183.99 into the address bar in browsers address bar. If this connects to Google's web page but still cannot connect to a website normally, we recommend attempting to connect to another Wi-Fi Network.
This will indicate if the issue is a handset fault or router related.
If even the DNS address does not allow a connection then we would advise removing the Wi-Fi Network from your handset. This can be performed as follows:
1. Open the Menu
2. Select Settings
3. Go in to Wi-Fi
4. Tap on your network
5. Forget Network
We would also suggest that you perform a full reset of your router. If you are unsure how this is performed, you will need to contact the manufacturer of the router.
If the handset simply cannot connect to any Wi-Fi Network then this suggests the handset itself is at fault and would suggest updating the software on your handset. This can be done free of charge using our Sony PC Companion tool via a Windows PC. To carry out the update you will need internet access and a USB cable.
It may be the case that user data is lost during this upgrade. We therefore recommend backing up any data to your SIM card, Memory Stick, or PC before upgrading.
Please follow the steps below to download and install the PC Companion software:
1. Go to www.sonymobile.com
2. Select Support
3. Choose your handset from the drop down list
4. Select "View All Software Updates"
5. Download for PC
6. Check the requirements and then "Download PC Companion"
Once you have installed the Sony PC Companion you will need to launch it. Once it opens connect your phone to your PC in Media Transfer mode and then go into Support Zone > Phone Software Update and then simply follow the instructions that you will see on screen. The update should then begin.
If you are unable to perform the software update on your PC as you do not have the requirements then you may be able to perform this from the handset itself by performing an 'Over the Air' update. This is available by following the steps below:
1. Open the Menu
2. Select Settings
3. Scroll down to About Phone
4. Tap on Software Update > Update Now
We would strongly suggest that you connect to Wi-Fi if you wish to update your handset in this way as this is a more secure connection and means no data charges will occur. Please also ensure you have a full battery when attempting the above.
If after performing the above the problem continues or your handset is already running the latest software available then you will need to perform a repair of the software using PC Companion.
To perform a repair of your handsets software, you will need to open PC Companion and then follow the below steps:
1. Go into Support Zone
2. Press “Start” for Phone Software Update
3. Click on “Repair Phone” from the pop-up box
When following the above steps, your handset must not be connected to the PC as the pop-up box you will receive gives an error saying there is no phone connected and then the option to select “Repair Phone”. If your phone is connected then you will not receive this message.
Once you have selected “Repair Phone” within PC Companion, simply follow the onscreen instructions as you will be asked to connect the phone to your PC at a later stage when it is powered off. Make sure the phone is not connected to the PC until you are asked to do so.
For the latest news, information and product support please visit www.sonymobile.com.
If you require any further assistance then please do not hesitate to respond to this email or call our customer support on 08705 237 237. Should you choose to contact us via an alternative channel, one of our agents will request a unique field from you and would suggest providing your Email address.
Please be aware that should you not respond within 5 days of this email your query will be automatically closed. Any further communications will not reach our support and a new query will need to be raised.
Kind Regards,
Adam Mottershead
Sony Xperia UK Customer Services
This does no help for this problem.
The problem will happen again and again.
Hello? Johan?
What's next?
I had PM to you many many days ago, and now?
I don't get any response, and no any useful information.
Is there anything that Sony have do for this problem?
Or you still think this is not important?
I am also experiencing the same issue with my Xperia Go. The issue was not existent prior to the ICS upgrade.
I have performed 3 "repairs" so far. The issue re-appears after a while. It is quite clear that we are dealing with a software issue. Something 'triggers' the faulty wifi. Sony must find out what this is and supply us with a patch to fix this.
It is a terrible issue that I have seen all over the forums and in many other sources. We cannot use wifi for god's sake. It is one of the most critical functions on a smartphone. It is ridiculous how this could have gone on for so long.
We CANNOT keep "repairing" the handsets. It takes too long to back everything up and then repair. It is just not practical and we are beyond sick of this.
Sony must support this issue ASAP. It has been going on for months now. It is unacceptable. I am very brand loyal to Sony normally with almost all my devices being Sony. I am however extremely disappointed with this subject to the point of looking elsewhere.
Sony, please respond. You have many people here practically begging for the help. Value your customers again please, before long you will not be seeing them again.
I also have the same problem as everyone else with Wifi being stuck after 5-10 minutes of use.
Unless Sony fixes this ASAP - or at least informs us whether they are actually working on the issue - I will change my mobile and never buy a Sony phone again.
I reinstalled ics with SUS for about 2 weeks, And when I was thinking that the problem was solved the problem returned!!
SONY ! SONY ! Respond and fix this problem ! this is a very good phone but with a deficient wireless is useless !!!
Do not ignore me and all these people with the same problem!
I found a way of turning it (wpa_suplicant) off without rebooting, or taking out the battery. This only work if the phone still has 3g connection to provider.
I start up the SSH server. Connect through a computer to my phone IP add, login, and do the following:
ps | grep wpa
-- this gives you the process number, and then..
kill 27473
and u can reconnect to wifi (for a short period of time, if you know what i mean)
is this rooted required?
man1ac, that workaround will propably take longer for most users to do than restarting their phone. 
However you have made a good point and you may have even provided Sony with a fix. (Although if it is as simple as that then they REALLY have been mocking us for not providing a solution up until now.)
Sony - are you able to build a wpa process killer / restarter in to your software so at least we can get back to using wifi?
Add it as a configurable setting e.g. 'Force Wifi Restart if not responding' check box or something along those lines if necessary.
Are there any applications out there that can do this I wonder? If anyone finds one pleae post here to share. (It better be a free app otherwise Sony - you will be getting the bills in the post from everyone!)