05.07: Debugging Tools for Linux Character Device Drivers - EmbLogic https://www.emblogic.com/forum/categories/05-07%3A-debugging-tools-for-linux-character-device-drivers/feed.rss Thu, 13 Aug 26 20:19:45 +0530 05.07: Debugging Tools for Linux Character Device Drivers - EmbLogic en-CA 05.07: Debugging Tools for Linux Character Device Drivers https://www.emblogic.com/forum/discussion/2164/05-07-debugging-tools-for-linux-character-device-drivers Mon, 18 May 2026 12:45:16 +0530 pravjot 2164@/forum/discussions All queries, discussions, updates and clarifications related to...
should be posted here.

]]> IQ: 005.07.50: Your character driver's `releaseDevice` function is crashing unexpectedly https://www.emblogic.com/forum/discussion/2215/iq-005-07-50-your-character-driver039s-releasedevice-function-is-crashing-unexpectedly Sat, 30 May 2026 17:28:48 +0530 pravjot 2215@/forum/discussions Interview Question: Your character driver's `releaseDevice` function is crashing unexpectedly, and you don't know which user-space application or kernel subsystem is invoking it. How can you use `ftrace` to discover the exact sequence of calls leading to `releaseDevice`?"]]> IQ: 005.07.49: You are reviewing an `ftrace` log and see a `!` symbol next to your `ioctl` https://www.emblogic.com/forum/discussion/2214/iq-005-07-49-you-are-reviewing-an-ftrace-log-and-see-a-symbol-next-to-your-ioctl Sat, 30 May 2026 17:20:30 +0530 pravjot 2214@/forum/discussions Interview Question: You are reviewing an `ftrace` log and see a `!` symbol next to your `ioctl` function's duration. What does this indicate, and how should it influence your debugging strategy?"]]> IQ: 005.07.48: Explain the workflow sequence involving `tracing_on` and your user-space test ... https://www.emblogic.com/forum/discussion/2213/iq-005-07-48-explain-the-workflow-sequence-involving-tracing_on-and-your-user-space-test- Sat, 30 May 2026 17:09:50 +0530 pravjot 2213@/forum/discussions Interview Question: Explain the workflow sequence involving `tracing_on` and your user-space test application, and why timing is critical during this process."]]> IQ: 005.07.47: When debugging a performance issue in your character driver, why would you choose https://www.emblogic.com/forum/discussion/2212/iq-005-07-47-when-debugging-a-performance-issue-in-your-character-driver-why-would-you-choose Sat, 30 May 2026 17:00:58 +0530 pravjot 2212@/forum/discussions Interview Question: When debugging a performance issue in your character driver, why would you choose `function_graph` over the standard `function` tracer?]]> IQ: 005.07.45: What would happen if you enabled the `function_graph` tracer and turned tracing https://www.emblogic.com/forum/discussion/2211/iq-005-07-45-what-would-happen-if-you-enabled-the-function_graph-tracer-and-turned-tracing Sat, 30 May 2026 16:48:05 +0530 pravjot 2211@/forum/discussions Interview Question: What would happen if you enabled the `function_graph` tracer and turned tracing on without first configuring `set_ftrace_filter` on a live system?]]> IQ: 005.07.44: What would happen if you enabled the `function_graph` tracer and turned tracin... https://www.emblogic.com/forum/discussion/2210/iq-005-07-44-what-would-happen-if-you-enabled-the-function_graph-tracer-and-turned-tracin- Sat, 30 May 2026 14:34:52 +0530 pravjot 2210@/forum/discussions Interview Question: What would happen if you enabled the `function_graph` tracer and turned tracing on without first configuring `set_ftrace_filter` on a live system?]]> IQ: 005.07.43: Where in the Linux filesystem hierarchy do you configure `ftrace`, ... https://www.emblogic.com/forum/discussion/2209/iq-005-07-43-where-in-the-linux-filesystem-hierarchy-do-you-configure-ftrace- Sat, 30 May 2026 13:49:53 +0530 pravjot 2209@/forum/discussions Interview Question: Where in the Linux filesystem hierarchy do you configure `ftrace`, and what permissions are required to modify these configuration files?]]> IQ: 005.07.42: How does the kernel manage to trace function calls using `ftrace` without... https://www.emblogic.com/forum/discussion/2208/iq-005-07-42-how-does-the-kernel-manage-to-trace-function-calls-using-ftrace-without- Sat, 30 May 2026 13:40:33 +0530 pravjot 2208@/forum/discussions Interview Question: How does the kernel manage to trace function calls using `ftrace` without causing a massive performance penalty when tracing is actually turned off?]]> IQ: 005.07.41: Explain the primary advantage of using `ftrace` over traditional logging macros like https://www.emblogic.com/forum/discussion/2207/iq-005-07-41-explain-the-primary-advantage-of-using-ftrace-over-traditional-logging-macros-like Sat, 30 May 2026 13:21:26 +0530 pravjot 2207@/forum/discussions Interview Question: Explain the primary advantage of using `ftrace` over traditional logging macros like `printk` when attempting to identify a performance bottleneck in a complex character device driver.]]> IQ: 005.07.41: What is the risk associated with failing to call `debugfs_remove_recursive` https://www.emblogic.com/forum/discussion/2206/iq-005-07-41-what-is-the-risk-associated-with-failing-to-call-debugfs_remove_recursive Sat, 30 May 2026 00:37:10 +0530 pravjot 2206@/forum/discussions Interview Question: What is the specific risk associated with failing to call `debugfs_remove_recursive` in your driver’s exit routine, and why is this specific function preferred over trying to remove individual files?

]]> IQ: 005.07.40: Write a simple code snippet to export an unsigned 32-bit counter in your driver as... https://www.emblogic.com/forum/discussion/2205/iq-005-07-40-write-a-simple-code-snippet-to-export-an-unsigned-32-bit-counter-in-your-driver-as- Sat, 30 May 2026 00:31:14 +0530 pravjot 2205@/forum/discussions Interview Question: Write a simple code snippet to export an unsigned 32-bit counter in your driver as read-only, and explain how you would configure a variable to be mutable (read-write) from user-space.

]]> IQ: 005.07.39: Why is putting random device driver debug data in `/proc` considered poor practice to https://www.emblogic.com/forum/discussion/2204/iq-005-07-39-why-is-putting-random-device-driver-debug-data-in-proc-considered-poor-practice-to Fri, 29 May 2026 23:55:39 +0530 pravjot 2204@/forum/discussions Interview Question: Why is putting random device driver debug data in `/proc` considered poor practice today, and how does `debugfs` differ philosophically from `sysfs`?]]> IQ: 005.07.38: Describe the dynamic debugfs API philosophy regarding error checking, and what happen https://www.emblogic.com/forum/discussion/2203/iq-005-07-38-describe-the-dynamic-debugfs-api-philosophy-regarding-error-checking-and-what-happen Fri, 29 May 2026 23:53:42 +0530 pravjot 2203@/forum/discussions Interview Question: Describe the dynamic debugfs API philosophy regarding error checking, and what happens if a failed directory pointer is passed to a function like `debugfs_create_u32`?

]]> IQ: 005.07.37: Describe the data flow that occurs inside the kernel when a user executes `cat` on... https://www.emblogic.com/forum/discussion/2202/iq-005-07-37-describe-the-data-flow-that-occurs-inside-the-kernel-when-a-user-executes-cat-on- Mon, 25 May 2026 18:23:18 +0530 pravjot 2202@/forum/discussions Interview Question: Describe the data flow that occurs inside the kernel when a user executes `cat` on a `debugfs` file that represents a 32-bit integer counter in your driver.]]> IQ: 005.07.36: Where does `debugfs` reside physically, and what happens to its structure when the... https://www.emblogic.com/forum/discussion/2201/iq-005-07-36-where-does-debugfs-reside-physically-and-what-happens-to-its-structure-when-the- Mon, 25 May 2026 18:18:21 +0530 pravjot 2201@/forum/discussions Interview Question: Where does `debugfs` reside physically, and what happens to its structure when the host system is rebooted?]]> IQ: 005.07.35: What does it mean to debug a driver 'out-of-band,' and why is this desirable when... https://www.emblogic.com/forum/discussion/2200/iq-005-07-35-what-does-it-mean-to-debug-a-driver-039out-of-band039-and-why-is-this-desirable-when- Mon, 25 May 2026 17:52:59 +0530 pravjot 2200@/forum/discussions Interview Question: What does it mean to debug a driver 'out-of-band,' and why is this desirable when managing complex driver memory structures?]]> IQ: 005.07.34: In a high-concurrency driver, why might relying on `printk` statements to debug a... https://www.emblogic.com/forum/discussion/2199/iq-005-07-34-in-a-high-concurrency-driver-why-might-relying-on-printk-statements-to-debug-a- Mon, 25 May 2026 17:47:41 +0530 pravjot 2199@/forum/discussions Interview Question: In a high-concurrency driver, why might relying on `printk` statements to debug a race condition be counterproductive, and what is this phenomenon called?]]> IQ: 005.07.33: Why is it critically important to remember to run `echo 'module my_module -p'` https://www.emblogic.com/forum/discussion/2198/iq-005-07-33-why-is-it-critically-important-to-remember-to-run-echo-039module-my_module-p039 Mon, 25 May 2026 15:46:41 +0530 pravjot 2198@/forum/discussions Interview Question: Why is it critically important to remember to run `echo 'module my_module -p'` on a production server after you have finished a live debugging session?]]> IQ: 005.07.32: What command would you use to list the status of all debug statements for `my_driver` https://www.emblogic.com/forum/discussion/2197/iq-005-07-32-what-command-would-you-use-to-list-the-status-of-all-debug-statements-for-my_driver Mon, 25 May 2026 15:41:52 +0530 pravjot 2197@/forum/discussions Interview Question: You have run several dynamic debug commands and want to check your work. What command would you use to list the status of all debug statements for `my_driver`, and what symbol indicates a statement is currently turned off?]]> IQ: 005.07.31: Explain the practical debugging benefit of using the `+pmfl` flags over the standard https://www.emblogic.com/forum/discussion/2196/iq-005-07-31-explain-the-practical-debugging-benefit-of-using-the-pmfl-flags-over-the-standard Mon, 25 May 2026 15:35:18 +0530 pravjot 2196@/forum/discussions Interview Question: Explain the practical debugging benefit of using the `+pmfl` flags over the standard `+p` flag when enabling dynamic debugs in a driver with thousands of lines of code.]]> IQ: 005.07.30: Your driver consists of `init.c`, `read.c`, and `write.c`. You suspect a memory... https://www.emblogic.com/forum/discussion/2195/iq-005-07-30-your-driver-consists-of-init-c-read-c-and-write-c-you-suspect-a-memory- Mon, 25 May 2026 15:22:32 +0530 pravjot 2195@/forum/discussions Interview Question: Your driver consists of `init.c`, `read.c`, and `write.c`. You suspect a memory leak in the write operation. How would you enable dynamic debugs only for the file handling the write operations to avoid log spam from constant reads?]]> IQ: 005.07.29: Write the exact terminal command you would use to globally enable all dynamic debug.. https://www.emblogic.com/forum/discussion/2194/iq-005-07-29-write-the-exact-terminal-command-you-would-use-to-globally-enable-all-dynamic-debug- Mon, 25 May 2026 14:55:11 +0530 pravjot 2194@/forum/discussions Interview Question: Write the exact terminal command you would use to globally enable all dynamic debug statements for a loaded driver module named `sensor_driver`.]]> IQ: 005.07.28: You are trying to echo commands into `/sys/kernel/debug/dynamic_debug/control` https://www.emblogic.com/forum/discussion/2193/iq-005-07-28-you-are-trying-to-echo-commands-into-syskerneldebugdynamic_debugcontrol Mon, 25 May 2026 14:45:35 +0530 pravjot 2193@/forum/discussions Interview Question: You are trying to echo commands into `/sys/kernel/debug/dynamic_debug/control` but are receiving a 'Permission denied' or 'No such file or directory' error. What are the two most likely system setup issues causing this?"]]> IQ: 005.07.27: If you have instrumented your character driver entirely with `pr_debug()` https://www.emblogic.com/forum/discussion/2192/iq-005-07-27-if-you-have-instrumented-your-character-driver-entirely-with-pr_debug Mon, 25 May 2026 14:37:02 +0530 pravjot 2192@/forum/discussions *nterview Question: If you have instrumented your character driver entirely with `pr_debug()`, why doesn't any output appear in `dmesg` immediately after you load the module with `insmod`, and what is the advantage of this behavior in a production environment?]]> IQ: 005.07.26: Why did the kernel developers transition away from using the `syslog(2)` system call https://www.emblogic.com/forum/discussion/2191/iq-005-07-26-why-did-the-kernel-developers-transition-away-from-using-the-syslog2-system-call Mon, 25 May 2026 14:06:50 +0530 pravjot 2191@/forum/discussions Interview Question: Why did the kernel developers transition away from using the `syslog(2)` system call to read the ring buffer in favor of the `/dev/kmsg` interface, and what capability does this give you as a user?]]> IQ: 005.07.25: Describe the step-by-step terminal commands you would use to completely isolate... https://www.emblogic.com/forum/discussion/2190/iq-005-07-25-describe-the-step-by-step-terminal-commands-you-would-use-to-completely-isolate- Mon, 25 May 2026 13:58:56 +0530 pravjot 2190@/forum/discussions Interview Question: Describe the step-by-step terminal commands you would use to completely isolate and view only the logs generated during the initialization of your driver `my_driver.ko`.

]]> IQ: 005.07.24: How would you monitor your character driver's log output in real-time while... https://www.emblogic.com/forum/discussion/2189/iq-005-07-24-how-would-you-monitor-your-character-driver039s-log-output-in-real-time-while- Mon, 25 May 2026 13:16:26 +0530 pravjot 2189@/forum/discussions Interview Question: How would you monitor your character driver's log output in real-time while simultaneously running a user-space C program to test its `read/write` functions?]]> IQ: 005.07.23: Explain what a 'print storm' is in the context of the Kernel Ring Buffer and why... https://www.emblogic.com/forum/discussion/2188/iq-005-07-23-explain-what-a-039print-storm039-is-in-the-context-of-the-kernel-ring-buffer-and-why- Sun, 24 May 2026 21:08:00 +0530 pravjot 2188@/forum/discussions Interview Question: Explain what a 'print storm' is in the context of the Kernel Ring Buffer and why logging from an Interrupt Service Routine (ISR) is generally discouraged.

]]> IQ: 005.07.22: If your `pr_info` statements don't appear on the terminal when you run `insmod`... https://www.emblogic.com/forum/discussion/2187/iq-005-07-22-if-your-pr_info-statements-don039t-appear-on-the-terminal-when-you-run-insmod- Sun, 24 May 2026 20:59:29 +0530 pravjot 2187@/forum/discussions Interview Question: If your `pr_info` statements don't appear on the terminal when you run `insmod`, where exactly does the kernel store them, and how would you retrieve them?]]> IQ: 005.07.21: If `class_create()` fails during your character driver's initial `__init` loading... https://www.emblogic.com/forum/discussion/2186/iq-005-07-21-if-class_create-fails-during-your-character-driver039s-initial-__init-loading- Sun, 24 May 2026 20:35:01 +0530 pravjot 2186@/forum/discussions Interview Question: If `class_create()` fails during your character driver's initial `__init` loading phase, should you log that specific failure using `pr_err` or `dev_err`? Justify your architectural choice.]]> IQ: 005.07.20: Describe the internal logic of `dev_err_probe()`. How does it differentiate between.. https://www.emblogic.com/forum/discussion/2185/iq-005-07-20-describe-the-internal-logic-of-dev_err_probe-how-does-it-differentiate-between- Sun, 24 May 2026 20:25:14 +0530 pravjot 2185@/forum/discussions Interview Question: Describe the internal logic of `dev_err_probe()`. How does it differentiate between a standard boot-time resource delay and a fatal initialization failure?]]> IQ: 005.07.19: What is the architectural purpose of `-EPROBE_DEFER` in the Linux kernel https://www.emblogic.com/forum/discussion/2184/iq-005-07-19-what-is-the-architectural-purpose-of-eprobe_defer-in-the-linux-kernel Sun, 24 May 2026 20:16:44 +0530 pravjot 2184@/forum/discussions Interview Question: What is the architectural purpose of `-EPROBE_DEFER` in the Linux kernel, and why does returning this code create logging challenges for driver developers?]]> IQ: 005.07.18: Explain a scenario in a custom character driver where using `dev_warn` is appropriate https://www.emblogic.com/forum/discussion/2183/iq-005-07-18-explain-a-scenario-in-a-custom-character-driver-where-using-dev_warn-is-appropriate Sun, 24 May 2026 17:22:16 +0530 pravjot 2183@/forum/discussions Interview Question: Explain a scenario in a custom character driver where using `dev_warn` is appropriate, but using `dev_err` would be technically or logically incorrect.]]> IQ: 005.07.17: If a user-space application sends a malformed or invalid ioctl command to your... https://www.emblogic.com/forum/discussion/2182/iq-005-07-17-if-a-user-space-application-sends-a-malformed-or-invalid-ioctl-command-to-your- Sun, 24 May 2026 17:13:32 +0530 pravjot 2182@/forum/discussions Interview Question: If a user-space application sends a malformed or invalid ioctl command to your hardware, which `dev_*` macro should you use to log this event, and why?]]> IQ: 005.07.16: justify implementing a `dev_alert` instead of a standard `dev_err` within your driver https://www.emblogic.com/forum/discussion/2181/iq-005-07-16-justify-implementing-a-dev_alert-instead-of-a-standard-dev_err-within-your-driver Sun, 24 May 2026 17:06:13 +0530 pravjot 2181@/forum/discussions Interview Question: Under what specific hardware or environmental circumstances would you justify implementing a `dev_alert` instead of a standard `dev_err` within your device driver code?]]> IQ: 005.07.16: What is the architectural difference bwn a `pr_err` and a `dev_err` macro https://www.emblogic.com/forum/discussion/2180/iq-005-07-16-what-is-the-architectural-difference-bwn-a-pr_err-and-a-dev_err-macro Sun, 24 May 2026 17:00:08 +0530 pravjot 2180@/forum/discussions Interview Question: What is the primary architectural difference in the function signature between a `pr_err` and a `dev_err` macro, and why is that specific difference mandatory for the Linux Device Model?"]]> IQ: 005.07.15: Explain how the `dev_*` macros leverage the Linux Device Model to improve upon... https://www.emblogic.com/forum/discussion/2179/iq-005-07-15-explain-how-the-dev_-macros-leverage-the-linux-device-model-to-improve-upon- Sun, 24 May 2026 16:27:37 +0530 pravjot 2179@/forum/discussions Interview Question: Explain how the `dev_*` macros leverage the Linux Device Model to improve upon standard `pr_*` logging functions, and what metadata they automatically inject into the kernel logs."]]> IQ: 005.07.14: If you have three identical custom USB devices plugged in and your driver relies... https://www.emblogic.com/forum/discussion/2178/iq-005-07-14-if-you-have-three-identical-custom-usb-devices-plugged-in-and-your-driver-relies- Sun, 24 May 2026 16:15:47 +0530 pravjot 2178@/forum/discussions Interview Question: If you have three identical custom USB devices plugged in and your driver relies exclusively on `pr_err` for I/O failures, what operational roadblocks does this create for a system administrator debugging a hardware fault?]]> IQ: 005.07.13: Suppose a customer reports a sporadic bug that you can't reproduce. https://www.emblogic.com/forum/discussion/2177/iq-005-07-13-suppose-a-customer-reports-a-sporadic-bug-that-you-can039t-reproduce- Sun, 24 May 2026 10:42:46 +0530 pravjot 2177@/forum/discussions Interview Question: Suppose a customer reports a sporadic bug that you can't reproduce. The customer cannot reboot their machine, nor recompile the kernel module. How would you leverage the existing `pr_debug` calls in your driver and Dynamic Debugging (`dyndbg`) to trace the bug on their live production server?]]> IQ: 005.07.12: Explain why logging from an Interrupt Service Routine (ISR) is discouraged https://www.emblogic.com/forum/discussion/2176/iq-005-07-12-explain-why-logging-from-an-interrupt-service-routine-isr-is-discouraged Sun, 24 May 2026 10:38:12 +0530 pravjot 2176@/forum/discussions Interview Question: Explain why logging from an Interrupt Service Routine (ISR) is discouraged in the Linux kernel and describe the negative system-wide consequences of a 'print storm' originating from a misconfigured driver logging at KERN_INFO level from an ISR.]]> IQ: 005.07.11: log via `pr_info` during its `init()` https://www.emblogic.com/forum/discussion/2175/iq-005-07-11-log-via-pr_info-during-its-init Sun, 24 May 2026 10:33:26 +0530 pravjot 2175@/forum/discussions Interview Question: Provide two examples of appropriate informational messages your custom driver should log via `pr_info` during its `init()` execution path.]]> IQ: 005.07.10: Why use `pr_notice` instead of `pr_info` to log successful cryptographic https://www.emblogic.com/forum/discussion/2174/iq-005-07-10-why-use-pr_notice-instead-of-pr_info-to-log-successful-cryptographic Sun, 24 May 2026 10:28:11 +0530 pravjot 2174@/forum/discussions Interview Question: Why use `pr_notice` instead of `pr_info` to log successful cryptographic key flush operations driven by user-space IOCTL calls?]]> IQ: 005.07.09:rate-limiting mechanism around `pr_warn` within a driver to prevent a malicious user.. https://www.emblogic.com/forum/discussion/2173/iq-005-07-09rate-limiting-mechanism-around-pr_warn-within-a-driver-to-prevent-a-malicious-user- Sun, 24 May 2026 10:20:17 +0530 pravjot 2173@/forum/discussions Interview Question: Explain how you would implement a rate-limiting mechanism around `pr_warn` within a driver to prevent a malicious user-space application from spamming the kernel log buffer via malformed IOCTLs.]]> IQ: 005.07.08: In a driver's `probe()` function, explain the standard sequence of events involving.. https://www.emblogic.com/forum/discussion/2172/iq-005-07-08-in-a-driver039s-probe-function-explain-the-standard-sequence-of-events-involving- Sun, 24 May 2026 10:15:10 +0530 pravjot 2172@/forum/discussions Interview Question: In a driver's `probe()` function, explain the standard sequence of events involving `pr_err` and the function's return value when a crucial memory allocation (e.g., `kzalloc`) fails.]]> IQ: 005.07.07: Assume your I2C-based character driver starts receiving constant checksum errors from https://www.emblogic.com/forum/discussion/2171/iq-005-07-07-assume-your-i2c-based-character-driver-starts-receiving-constant-checksum-errors-from Sun, 24 May 2026 10:03:22 +0530 pravjot 2171@/forum/discussions Interview Question: Assume your I2C-based character driver starts receiving constant checksum errors from a sensor. Explain a robust error-handling flow that would culminating in a `pr_crit` invocation.]]> IQ: 005.07.06: How does the intended response to a `pr_alert` message differ from ... https://www.emblogic.com/forum/discussion/2170/iq-005-07-06-how-does-the-intended-response-to-a-pr_alert-message-differ-from- Sun, 24 May 2026 09:35:40 +0530 pravjot 2170@/forum/discussions Interview Question: How does the intended response to a `pr_alert` message differ from the intended response to a `pr_crit` message in a production environment?]]> IQ: 005.07.05: In what scenario would custom character driver ever be justified in using `pr_emerg` https://www.emblogic.com/forum/discussion/2169/iq-005-07-05-in-what-scenario-would-custom-character-driver-ever-be-justified-in-using-pr_emerg Sun, 24 May 2026 09:27:26 +0530 pravjot 2169@/forum/discussions Interview Question: In what specific scenario would a custom character driver ever be justified in using `pr_emerg`, and how does this log level behave differently concerning standard kernel buffering mechanisms?]]> IQ: 005.07.04: using `pr_*` macros instead of invoking raw `printk()` with KERN priority https://www.emblogic.com/forum/discussion/2168/iq-005-07-04-using-pr_-macros-instead-of-invoking-raw-printk-with-kern-priority Sun, 24 May 2026 09:19:24 +0530 pravjot 2168@/forum/discussions Interview Question: Explain the technical benefits, beyond code readability, of using `pr_*` macros instead of invoking raw `printk()` with KERN priority constants within a Linux device driver.

]]> IQ: 005.07.03: when you insert the module using insmod, you don't see this message on your... https://www.emblogic.com/forum/discussion/2167/iq-005-07-03-when-you-insert-the-module-using-insmod-you-don039t-see-this-message-on-your- Sun, 24 May 2026 00:34:38 +0530 pravjot 2167@/forum/discussions Interview Question: "Suppose you instrument your character driver with printk(KERN_DEBUG "Driver initialized\n");,

but when you insert the module using insmod, you don't see this message on your console, though you do see KERN_ERR messages. What kernel mechanism is controlling this visibility, and how would you adjust the system to see your debug messages?"

]]> IQ: 005.07.02: what happens if you call printk() from within a high-frequency hardware interrupt... https://www.emblogic.com/forum/discussion/2166/iq-005-07-02-what-happens-if-you-call-printk-from-within-a-high-frequency-hardware-interrupt- Sun, 24 May 2026 00:27:49 +0530 pravjot 2166@/forum/discussions Interview Question: You mentioned printk() is the standard for kernel logging. Since the kernel can be preempted or interrupted, what happens if you call printk() from within a high-frequency hardware interrupt handler (ISR)? Is it safe, and what are the potential performance implications?

]]> IQ.005.07.01. Since the Kernel Ring Buffer is a circular buffer that continuously overwrites old... https://www.emblogic.com/forum/discussion/2165/iq-005-07-01-since-the-kernel-ring-buffer-is-a-circular-buffer-that-continuously-overwrites-old- Sun, 24 May 2026 00:12:49 +0530 pravjot 2165@/forum/discussions Interview Question: Since the Kernel Ring Buffer is a circular buffer that continuously overwrites old data, how might this impact your ability to debug a sporadic hardware issue that crashes the system overnight, and how would you ensure those logs aren't lost?

]]>