High DPC Latency bug is back

copypasta from the “bug template” :slight_smile:

The bug/issue

  1. What you did: Well basically I started downloading a torrent. It was downloading at around 1.1MB/s (max). However this issue also appears when I’m not downloading anything and just seeding stuff.
  2. What actually happened or you actually saw: I saw lots of red bars in dpclat.exe The sound became choppy, started stuttering. Every second (or, at the best, every few seconds), there’s a sound stutter. Just as in all dpc latency issues.
  3. What you expected to happen or see: I expected to see… literally nothing. Well apart from green bars in dpclat.exe
  4. How you tried to fix it & what happened: I thought it might be a small network traffic monitoring app (skin for Rainmeter), but disabling it didn’t fix it, so that’s not it. After quitting the torrent app it goes back to normal. More or less.
  5. Whether you can make the problem happen again, and if so exact steps to make it happen: Of course I can, it’s enough to start a torrent app and grab any torrent with good speeds.
  6. Any other information (eg your guess regarding the cause, with reasons): It is just like long, long time ago, when Comodo CIS (I think it was 4.x) had those DPC latency issues. It’s been fixed before, and now it’s back :confused: (I haven’t updated network drivers since that time as there aren’t any newer). I think it started happening after last (or the one before) Comodo CIS update (which, by the way, was somewhat faulty, it told me to update like 7 times before it actually decided it’s updated already…)

Files appended. (Please zip unless screenshots).

  1. Screenshots illustrating the bug:


Your set-up

  1. CIS version, AV database version & configuration used: 5.3.176757.1236
  2. Defense+, Sandbox, Firewall & AV security levels: D+=disabled , Sandbox=disabled , Firewall = safe, AV = not installed
  3. OS version, service pack, number of bits, UAC setting, & account type: Windows 7 Professional, x64, UAC enabled, administrator account

UPDATE: of course, if I hit Exit in the torrenting app, I get a nice FREEZE of the OS for a few seconds, when the sound is so choppy it’s like listening to a machine gun. Even mouse is stuttering, actually everything is stuttering then, absolute maximum dpc jumps to (at least) 41000 us, and then a minute or so after exiting the torrent app the graph is all nice and green:


(and guess what, the sound isn’t choppy anymore)
So, as I said, it’s something that has been fixed already, but then it reappeared…

Did this happen with the CIS 5.0 before the update?

Also what is the name of the torrent application you used?

I can’t say for sure that it wasn’t happening before (I remember getting irritated by that many times in the past), but there was a long, nice time when I didn’t have any of those DPC latency issues (and as far as I recall, I didn’t have those issues right after the new interface/skin was introduced, which I think makes it 5.0). I guess I wouldn’t mind installing an older version to check it though.

The torrent app I’m using is uTorrent.
It’s been running for a while now, here are statistics since launching:

uploaded: 800MB
downloaded: 30MB
incoming connections since app start: 4013
outgoing connections since app start: 21919
connections: 21
uTP: 1
half-open: 4

I’m uploading at around 20kB/s and the dpc latency chart is, well, I’d say kinda bad…


I bet if I started downloading something now, latencies would go sky-high :slight_smile:

It would be really helpful if you can give us some statistics such as:

DPC latency increase in a specified amount of time with 5.3 and 5.0. How long does it take for DPCs to increase to red levels?

Hmm, this might take a while to investigate, I’ll probably post the results in a few days.

Thanks for helping us get ot the bottom of this. Much appreciated. :-TU

Hi dark_skeleton,

This is a serious bug based on your description,but I can’t reproduce the issue successfully in our lib, I want to you help me test some patches file, so I can locate the point and address it. my msn is: greenfield_wang@hotmail.com, if you fell free, please contact me any time.

Thanks for your kindly help!

Rick ■■■■

I confirm DPC is back since version 5.3.175888.1227, at least in my case.

This is what I wrote on News section:

“Hello everyone!
I’m new here but I’m using Comodo Firewall since v2 and I want to say you’re doing a great job!
I have a problem, I’m using Comodo Firewall 5.3 and after the update to 5.3.175888.1227 was applied, I started having problem with DPC Latency, after 8 hours and >8 GB upload with utorrent, DPC Latency variates between 5000-16000 microseconds. If I disable network card or close utorrent, problem disappears. I don’t know exactly in which version this bug was present, I think it was last year and I had the same problem with that version.
Can anyone confirm this bug or my problem is caused by another software program? Huh
My specs: Windows 7 x64+SP1, avast! 5.1.889, Comodo Firewall 5.3.175888.1227, utorrent 2.2, latest Realtek drivers for network card.
Thank you!”

So, after approximately 3-3,5 hours DPC is showing 2000-3000 microseconds. I think DPC latency increases directly proportional with the amount of network traffic or connections number.
First, I uninstalled avast and problem didn’t disappear, it did after I uninstalled Comodo. That day utorrent downloaded 8GB and uploaded 100GB and DPC Latency was <500 microseconds.

I hope this bug will be fixed with next update.

[attachment deleted by admin]

Hmm okay, so here’s as I promised:
Comodo CIS v5.3.176757.1236 (latest)

uTorrent running for around 5.5 hours (you can see the launch date/time highlighted in the video, as well as current system time and what happens when I start downloading ubuntu (max speed is 1.2MB/s)
Now if I exit uTorrent and start it again and start downloading ubuntu,it behaves like this:
it looks better, but still far, far from perfection.

I’m gonna leave uTorrent running for 12h+ and report back with another video tomorrow.

EDIT: Oh wait, this is funny. Now Comodo updater tells me there’s even newer version of CIS… what the hell… you guys need to update Comodo Firewall | Get Best Personal Firewall Software for $29.99 A Year more frequently (I’m currently using a version that’s not even listed there…) ;]
EDIT2: False alarm, Comodo Updater fails.

RickWang asked me to turn off Comodo driver, so here it is.

[attachment deleted by admin]

Confirmed I had this DPC latency issue with Comodo before and now it is back, please fix it!!

For what it’s worth I can cause DPC latency to increase to unacceptable levels simply by maximising the uTorrent window. Maximise the uTorrent window, latency constantly hits 4000, minimise the window to the system tray, latency instantly reduces to well below 500. This is reproducible always.

This is regardless of the number of torrents being uploaded/downloaded, or the speed with which the transfers take place.


Latest Comodo Firewall 5 (firewall only), latest Avira Premium Security Suite 10 (without firewall), utorrent 2.0.4 build 22967 (configured for max speed), Win7 x64, AMD Athlon 64 X2 6000+ 3000 MHz, 4GB DDR2, Asus M2N, connect speed U/D 8MBit/s / 80MBit/s.

For a couples of days i noticed some troubles while listening MP3 with foobar, jetaudio. Same problems occurred while playing youtube video. After some hours of searching i found DCP Latency Checker. 18000+ ms after 10+ hours of running utorrent (it was yesterday). After utorrent was restarted, DCP is about < 500 ms, after 1 hour of running utorrent DCP >= 2000 ms. Then i found this topic. Uninstalled Comodo Firewall. Right now DCP <= 500 ms (peak 698 ms), after 2 hours of running utorrent.

By the way… Comodo update wizard was false positive all the time…

Hope you’ll fix it, because right now i’m without firewall =\

PS sorry for my bad english (:

Ok guys, Rick ■■■■ helped me solve this annoying bug, once again thank you Rick!

This are the steps you must follow:

  1. Download attached file (Comodo.rar) and extract it;
  2. Open folder “windows\system32\drivers”;
  3. Rename cmdhlp.sys to cmdhlp.sys.org;
  4. Copy the attached file named cmdhlp.sys to the folder;
  5. Run “dseo13b.exe” (Driver Signature Enforcement Overrider), choose “Enable Test Mode” and then click Next;
  6. Reboot;
  7. After log on you should see a watermark (Test Mode) down in the right corner above task bar. Run “dseo13b.exe”, choose “Sign a system driver”, click Next, insert the address for cmdhlp.sys (c:\windows\system32\drivers\cmdhlp.sys) then click Ok. It will tell you that the ssytem file has been signed successfully;
  8. Choose “Remove watermarks” and click Next. This option will remove “Test Mode” watermark;
  9. Reboot;

Now, Comodo should work fine without DPC problem. It does for me! :slight_smile:
They know what driver causes the problem and I think they will fix it with the next update.

Good luck!

LE: I forgot to tell you, Comodo Updater will show you that new update is available, ignore this unless the new version is >5.3.176757.1236!

[attachment deleted by admin]

Sorry, this may be genuine, but I have no idea who Rick ■■■■ is, or who you are. Please provide something better.

Rick ■■■■ is a member of Comodo’s staff.
It’s your choice Radaghast, I don’t force anyone to replace cmdhlp.sys driver, but I don’t understand what are you afraid of. ???

0but I don't understand what are you afraid of. Huh;

I’m not afraid of anything, mostly. But I’d prefer some corroboration from a legitimate source before I download a patch to my main security product…

I can verify the source is valid.
Rick is indeed a Comodo staff member and Comodo Engineer.

Indeed, the Pope could be too. The patch could be anything…