Ubuntu 20.04 freezes for no apparent reason, media continues to play, mouse moves but click doesn’t work

… tired of running out of resource, two months ago I moved Ubuntu (new install) 20.04 on a HP ZBook 15 G6, Intel Quad-core CPU, with 48GB RAM, thinking it will never run out of RAM or CPU usage.

But already twice, the system seems to freeze for no apparent reason, the media (my Udemy course) continue to play. The mouse moves, but not reacting to clicking. Even my Virtualbox lab processes seem to be running, except I can’t access them.

I have to press the power button to do a cold start. Below is the output from lspci. Does any of them raise an alarm?

thanks much for sharing any insight!

0:00.0 Host bridge: Intel Corporation 8th Gen Core Processor Host Bridge/DRAM Registers (rev 0d)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor PCIe Controller (x16) (rev 0d)
00:04.0 Signal processing controller: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Thermal Subsystem (rev 0d)
00:12.0 Signal processing controller: Intel Corporation Cannon Lake PCH Thermal Controller (rev 10)
00:13.0 Serial controller: Intel Corporation Device a37c (rev 10)
00:14.0 USB controller: Intel Corporation Cannon Lake PCH USB 3.1 xHCI Host Controller (rev 10)
00:14.2 RAM memory: Intel Corporation Cannon Lake PCH Shared SRAM (rev 10)
00:15.0 Serial bus controller (0c80): Intel Corporation Cannon Lake PCH Serial IO I2C Controller #0 (rev 10)
00:15.1 Serial bus controller (0c80): Intel Corporation Cannon Lake PCH Serial IO I2C Controller #1 (rev 10)
00:16.0 Communication controller: Intel Corporation Cannon Lake PCH HECI Controller (rev 10)
00:16.3 Serial controller: Intel Corporation Cannon Lake PCH Active Management Technology – SOL (rev 10)
00:17.0 SATA controller: Intel Corporation Cannon Lake Mobile PCH SATA AHCI Controller (rev 10)
00:1c.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #3 (rev f0)
00:1c.4 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #5 (rev f0)
00:1d.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #9 (rev f0)
00:1d.5 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root Port #14 (rev f0)
00:1f.0 ISA bridge: Intel Corporation Device a30e (rev 10)
00:1f.3 Multimedia audio controller: Intel Corporation Cannon Lake PCH cAVS (rev 10)
00:1f.4 SMBus: Intel Corporation Cannon Lake PCH SMBus Controller (rev 10)
00:1f.5 Serial bus controller (0c80): Intel Corporation Cannon Lake PCH SPI Controller (rev 10)
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (7) I219-LM (rev 10)
01:00.0 VGA compatible controller: NVIDIA Corporation TU117GLM (Quadro T1000 Mobile) (rev a1)
01:00.1 Audio device: NVIDIA Corporation Device 10fa (rev a1)
02:00.0 Unassigned class (ff00): Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
05:00.0 PCI bridge: Intel Corporation JHL7540 Thunderbolt 3 Bridge (Titan Ridge 4C 2018) (rev 06)
06:00.0 System peripheral: Intel Corporation JHL7540 Thunderbolt 3 NHI (Titan Ridge 4C 2018) (rev 06)
3a:00.0 USB controller: Intel Corporation JHL7540 Thunderbolt 3 USB Controller (Titan Ridge 4C 2018) (rev 06)
6f:00.0 Non-Volatile memory controller: SK hynix Device 1627
70:00.0 Network controller: Intel Corporation Wi-Fi 6 AX200 (rev 1a)

iphone – How do you exit guided access when it freezes?

iphone – How do you exit guided access when it freezes? – Ask Different

c# – Unity freezes when running BFS update instead of visualizing each step

Your code is written under the assumption that the player can see directly into the memory of the program as it’s running. So as long as you change a variable, the player should be able to immediately observe that change, like if you’d flipped a physical card on the table in front of them.

Games don’t work that way. If we want a player to see something change in our world, we need to draw it to an image and put that image on the player’s screen first. That takes some work from the CPU to initiate. And the CPU can’t do that work if it’s busy doing something else.

A typical game loop looks something like this, in a simplified model:

  1. Process window messages – this is what keeps the application from hanging, and allows it to read user input provided from the OS

  2. Update the game state, running any per-object update scripts

  3. Render the resulting frame and present it to the screen

  4. Sleep until it’s time for the next frame

This most often runs single-threaded, and that’s the case for the Unity game loop too. (Even systems that use threading typically use it to “go wide” in a single step, like running multiple non-conflicting state updates in parallel in step 2, while still finishing all step 2 work before taking a state snapshot to render in step 3)

So, as long as you’re keeping the CPU busy in step 2, it never gets to step 3, so you never get to see an intermediate state rendered. And it also never gets back to step 1, which is what makes the app go unresponsive until your script finishes its work.

The culprit is your MyDelay function:

public static void MyDelay(float seconds)
{
    DateTime dt = DateTime.Now + TimeSpan.FromSeconds(seconds);
    do { } while (DateTime.Now < dt);
}

This is what’s called a “Busy Wait” – it tells the CPU to sit there checking and re-checking the time, burning millions of cycles doing nothing useful at all, until it’s allowed to continue on to the next line of code. You’ve temporarily suspended any real processing and turned this CPU core into a space heater.

(There are times when a busy wait is appropriate, when you think you’ll very likely be waiting less time than it takes to sleep and wake a thread. A busy loop running for a hundredth of a second as you have here is never a good idea, and you should throw away any tutorial that told you to do that)

Because you’ve kept this thread busy this whole time, it’s not allowed to exit step 2 and continue on to step 3, rendering your changes for the player to see them, until the whole routine has finished. At that point it shows only the finished state.

The better way to do something like this in Unity is to use Coroutines. This is a function that can run partially, then yield control flow back to the code that called it, so the CPU can finish the rest of step 2 and draw it in step 3. Then, in the next iteration of the game loop, the calling code can resume your coroutine right where it left off, and continue until the next yield. In this way it takes turns with all the other work needed to update and render your scene, rather than hogging the CPU to itself until it’s finished.

MySQL freezes every hour at the exact same time

We have an hard-to-understand issue with our production MySQL RDS 8.0.20 instance.

Problem:

  • Every hour, at the exact same time, at :00 we experience a database glitch. Sometimes it’s big and customers are affected, sometimes it’s not, but we always see a glitch.

    By big I mean it could be few seconds or even up to 10 seconds, by small I mean it could be second or so.
    What is a glitch? Well, our java application fires the following sequences:

  1. set autocommit = 0
  2. Then makes insert(s) / update(s) / select(s)
  3. commit

So what we see, is that this exact COMMIT sql takes lots of time.
Literally, in our slow query logs, we see 10s or 20s COMMITs.
To put it simply: selects, inserts, updates go fast, COMMITs are stuck.
Once an hour, at :00.

Observations:

  • In performance insights, we see that there is a spike, every hour, at the exact time of a glitch. wait/sync/cond/sql/MYSQL_BIN_LOG::COND_done contributes to this spike.
    The queries are in status “waiting for handler commit”.

  • There is an increased database connections at this time, but this is normal & expected: if application continues to receive http requests and some database connections from the conn. pool are stucked, then application starts to open new connections.

  • We noticed that there is a minor spike in Write Latency ( it’s visible in RDS console ).
    It’s usually 3ms, but it jumps to 8ms. We suspect that it may have a big/huge value during the glitch, but it’s 8ms because it’s averaged for a minute. Unfortunately, the minute of granularity seems the maximum.

  • We haven’t noticed any other change of metrics. Disk IO, CPU, innodb reads / writes / updates look good, both from normal monitoring and from the performance insights look good. We haven’t even noticed anything in Enhanced monitoring. Write IOPS is 600, Read IOPS is 300, Queue Depth is 0.75. They sometimes jumping due to the heavy read SQLs, but they are very stable +- during the glitch.

  • We don’t see anything unusual in innodb_rows_read.avg, innodb_rows_updated.avg, innodb_rows_deleted.avg and innodb_rows_inserted.avg. Basically, during the time of a glitch, +- 2 minutes these metrics are usual, which means that there is no any special activity going during this time.

  • We have also reviewed all our cron jobs etc, it doesn’t look to us that there is anything happening in the database which contributes to this glitch.
    There are increased locks at this time, but I think it’s also expected: queries are waiting for lock on binlog.

  • We have innodb_flush_log_at_trx_commit = 2 and sync_binlog = 0. We have innodb_log_file_size = 134217728, which is 134 MB. I know, it’s a bit small and could be made 1GB, but since the issue happens at exact time without any insert / update / delete activity, I doubt it’s connected.

  • There are no other slow query logs ( > 1s ) at the time or before the time.

  • A bit of data from SHOW ENGINE INNODB STATUS ( run at normal time when there is no issue but a good production load ):

7174379566 OS file reads, 
10959861316 OS file writes, 
1045626171 OS fsyncs
215.88 reads/s, 
16384 avg bytes/read, 
1249.28 writes/s, 
128.21 fsyncs/s
482.54 inserts/s, 
210.98 updates/s, 
48.02 deletes/s, 56656.29 reads/s
Number of system rows inserted 10524, 
updated 61130, deleted 6743, read 66988909
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 17.58 reads/s

MySQL freezes every hour at exact time

MySQL freezes every hour at exact time – Database Administrators Stack Exchange

display – Screen freezes but mouse/keyboard/sound working

Lately I have been experiencing screen freezes when I am playing some games. Screen is locked, only mouse pointer moves. I can still hear and talk through vc and have sound from game. Keyboard is also working( I tested alt+tab + random gibberish on notes and it was saved). Until today I thought that only workaround is to force reboot my Mac but today I tried replugging my monitors and it worked too. I have m1 Mac mini from release day and this problem only showed about 1-2 weeks ago.

My setup:

  • Mac mini m1
  • 1 monitor -> hdmi -> Mac mini
  • 1 monitor -> hdmi -> usb-c hub -> Mac mini

This happens mostly when playing some games, not all thought.

Having workaround to replug cables is fine for now but I would prefer to fix it.

Ubuntu 20.4 crashes / freezes whenever there is yet another update

I’m running Ubuntu 20.4, and I had set my update-options to “weekly” (security updates “display immediately”), the live patch option was switched off.
Whenever there is an update (security, Ubuntu, just Google browser…), the whole system freezes and is unresponsive. This is especially annoying if you’re waiting for a calculation that already took all day, return to your machine in the morning and see … it’s crashed… once again

It’s great that people are working so hard to improve the system and everything… But could you PLEASE add an option to TURN OFF updates completely (yes, the security updates as well)?

And my questions:

  • Is there a way to disable the updates completely (I set it to “never” now, but there is no way to get rid of the security options, disconnecting my machine from the internet is no option as it uses access to databases for the calculations I need to do)

  • Is there a way to get the crash log after the restart?

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