Soft Lockup CPU Stuck – Causes And Fixes In 2025!
Dealing with a soft lockup on your CPU can be incredibly frustrating, especially when your system freezes or becomes unresponsive for no apparent reason.
A soft lockup occurs when a CPU gets stuck due to a Linux kernel bug, causing repeated freezing or unresponsiveness. It typically happens when the CPU fails to complete a task, leading to performance issues.
This article will explain a soft lockup, why it happens, and most importantly, how to fix it. Whether it’s a software issue, a hardware malfunction, or overclocking gone wrong, we’ve got you covered with practical solutions to get your system back on track.
What is a Soft Lockup?
A soft lockup happens when the CPU gets stuck doing one task too long and doesn’t allow other processes to run. This usually occurs if a program or the system uses all the CPU power without a break.
Linux systems detect soft lockups when the CPU fails to respond within 10 seconds. Unlike a hard lockup, the system doesn’t fully crash, but it slows down significantly, making it difficult to use properly.
Technical Mechanism Behind Soft Lockups

The kernel employs a watchdog process for each CPU to monitor its activity. This process periodically wakes up, records a timestamp, and saves it in a per-CPU data structure.
An interrupt function, softlockup_tick(), compares the current time to the saved timestamp. A soft lockup is reported if the difference exceeds a threshold (commonly 10 seconds). This mechanism ensures that no single process can monopolize the CPU to the detriment of system responsiveness.
How Does a Soft Lockup Happen?
The Linux kernel watchdog process detects soft lockups, which continuously checks whether CPUs are operating correctly. Here’s how it works:
- A watchdog thread runs on each CPU and updates a timestamp regularly.
- A separate monitoring process checks these timestamps.
- If a CPU fails to update its timestamp within the expected 10-second window, the kernel assumes a soft lockup has occurred.
Also Read: CPU Speed 1.1 GHz – Speed, Efficiency And Use Cases!
Common Causes of Soft Lockups
Soft lockups happen when the CPU runs a task too long without switching to other processes. Below are the most common reasons why this occurs:
1. High CPU Usage by a Single Process
When a program or system task consumes 100% of the CPU, it can prevent other processes from running. This often happens due to poorly optimized code, infinite loops, or heavy background tasks.
2. Kernel Bugs and Deadlocks
Errors in the Linux kernel can cause the CPU to freeze. Deadlocks happen when two or more tasks wait for each other to finish, creating an endless loop where nothing moves forward.
3. Faulty or Incompatible Drivers
Old or mismatched drivers can make the CPU unresponsive. When a driver fails, the system may keep trying to communicate with a device that isn’t responding, leading to a lockup.
4. Hardware Issues (CPU, RAM, or Overheating)
A failing CPU, defective RAM, or overheating system can cause soft lockups. If the CPU gets too hot, it may struggle to complete tasks properly, leading to slow performance and freezes.
5. Resource Starvation and Kernel Overload
If a system runs too many tasks with insufficient CPU or memory, essential processes may get delayed, leading to watchdog warnings and soft lockups. This is common in heavily loaded servers.
Identifying Soft Lockup Issues
Detecting soft lockups involves monitoring system logs and CPU activity:
- System Logs: Messages indicating soft lockups are typically logged in /var/log/messages or /var/log/syslog. These logs provide details about the affected CPU and process.
- Monitoring Tools: Utilities like top, htop, and vmstat can help identify processes consuming excessive CPU time. Additionally, commands like dmesg can display kernel messages related to soft lockups.
Impacts of Soft Lockups

Soft lockups can slow down or completely disrupt a system, affecting personal and business operations. Here are the key impacts:
1. System Unresponsiveness
When a soft lockup occurs, the system becomes extremely slow or unresponsive. You may notice delays when typing, clicking, or opening programs. In severe cases, you might need to force a restart.
2. Data Loss and Corruption
Important files may become corrupted or lost if a lockup happens while saving files or updating data. This can be risky for businesses handling critical information.
3. Service Downtime
For servers and enterprise systems, soft lockups can cause website crashes, failed transactions, and interrupted services. This can lead to customer dissatisfaction and financial losses.
4. Increased Hardware Stress
A constantly overloaded CPU generates excessive heat, which can shorten the lifespan of components like the processor, motherboard, and RAM, leading to potential hardware failure.
5. Security Vulnerabilities
Soft lockups can expose security weaknesses. If a system is stuck and unable to process security updates, it becomes vulnerable to cyber threats, malware, and hacking attempts.
Must Read: Inventory Agent High CPU: Step-by-Step Guide to Fix – 2025!
Advanced Fixes for Soft Lockup
1. Disabling Overclocking
Overclocking pushes your CPU to run faster than its factory settings, which can sometimes cause instability and lead to soft lockups. If you’ve overclocked your system to improve performance, it may be causing your CPU to become overloaded.
A. How to Disable Overclocking:
- BIOS Settings: You can disable overclocking by entering the BIOS/UEFI settings when you boot your system (usually by pressing “F2” or “Delete”). Look for options related to CPU speed or clock multipliers and set them back to the default settings.
- Software Tools: If you use software like MSI Afterburner or Intel XTU to overclock your system, you can adjust the settings within these tools to return your CPU to its original speed.
Turning off overclocking may cause a slight decrease in performance but will often restore stability and prevent soft lockups.
2. Reinstalling Software
Sometimes, soft lockups occur due to conflicts or corrupt files within specific software applications. If a program triggers the issue, reinstalling it can help fix the underlying problem.
A. How to Reinstall Software:
- Uninstall the Software: Go to “Control Panel” > “Programs and Features” (Windows) or “Applications” (Mac) and uninstall the problematic software.
- Clean Up Residual Files: After uninstalling, it’s a good idea to use tools like CCleaner to remove leftover files that might be causing issues.
- Reinstall the Software: Download the latest version of the software from the official website and reinstall it. Make sure it’s compatible with your system version to avoid future conflicts.
This fix can resolve soft lockups caused by software bugs or outdated versions.
3. Replacing Faulty Hardware
If your CPU or another hardware component malfunctions, it can trigger soft lockups. Common culprits include faulty RAM, a failing hard drive, or overheating components. Replacing or testing these parts can help restore stability.
A. How to Check for Faulty Hardware:
- Run Memory Diagnostics: Use Windows’ built-in Memory Diagnostic tool or MemTest86 to check your RAM for errors.
- Check for Hard Drive Issues: Run disk checks using built-in tools like CHKDSK or third-party programs such as CrystalDiskInfo to assess the health of your hard drive.
- Check Temperatures: Use hardware monitoring software like HWMonitor or Core Temp to check your CPU and GPU temperatures. Overheating components can lead to soft lockups.
If any component is showing signs of failure, replacing it will likely resolve the issue.
Resolving And Preventing Soft Lockups
To address and prevent soft lockups:
- Update the Kernel: Ensure the system is running the latest stable kernel version, as updates often include fixes for known issues.
- Optimize Application Code: Review and optimize applications to prevent excessive CPU usage. Implement proper error handling to avoid infinite loops.
- Monitor System Resources: Regularly monitor CPU and memory usage to identify potential bottlenecks. Adjust resource allocations as needed.
- Check Hardware Health: Regularly test hardware components for faults. Replace any defective parts promptly.
- Update Drivers: Ensure all hardware drivers are up-to-date and compatible with the system.
- Adjust Kernel Parameters: Tuning kernel parameters related to process scheduling and resource allocation can help prevent soft lockups.
Soft Lockup – CPU Stuck in VirtualBox

A soft lockup in VirtualBox happens when the guest system gets stuck using all CPU power and doesn’t respond properly.
This can be caused by high CPU load, misconfigured settings, or outdated VirtualBox versions. To fix it, try allocating more CPU cores, updating VirtualBox, or adjusting virtualization settings like enabling Nested Paging.
Soft Lockup – CPU Stuck in VMware
A soft lockup happens in VMware when the virtual machine (VM) stops responding due to high CPU usage or kernel issues.
This can occur if the host system lacks enough resources. To fix it, try increasing CPU allocation, updating VMware tools, or checking for kernel updates to prevent CPU stalls inside the VM.
Read Out: Not Enough CPU For Conversion Of This Item – Quick Fixes!
Watchdog Bug – Soft Lockup CPU Stuck
A watchdog bug happens when the Linux kernel detects a CPU is stuck and hasn’t responded in time. This can be due to high CPU usage, kernel bugs, or faulty drivers.
To fix it, try modifying the watchdog timeout, updating the kernel, or checking system logs for faulty processes that may be causing the issue.
FAQs
1. What is the difference between a soft lockup and a hard lockup?
A soft lockup allows limited system functionality, while a hard lockup completely freezes the system, requiring a restart.
2. Can a soft lockup cause data loss?
In most cases, no. However, frequent crashes can lead to file corruption, so it’s essential to back up important data regularly.
3. Is overclocking the main cause of soft lockups?
Overclocking can cause instability, but other factors like software conflicts and hardware issues are also common causes.
4. How do I check if my CPU is overclocked?
You can use software tools like CPU-Z or your BIOS settings to check if your CPU runs at overclocked speeds.
5. Should I worry if my system occasionally experiences a soft lockup?
Occasional soft lockups might not be a significant concern, but frequent occurrences may indicate an underlying issue that needs addressing.
Conclusion
In conclusion, soft lockups can severely impact system performance, but understanding their causes and solutions can help resolve and prevent them. Regular updates, hardware checks, and optimized configurations can significantly reduce the likelihood of recurring issues.
Post Comment