A work item can be blocked by a dependency that is queued correctly but cannot become active under the workqueue’s admission limit. Adding worker threads does not necessarily solve that condition. First identify the queue, effective concurrency domain and release dependency, then show whether the required producer can obtain an active slot. This article uses…
A guard page can turn a kernel stack access beyond the mapped stack into an immediate fault, but it does not detect every bad write within that stack. Diagnose a guard-page report by establishing which stack and address were involved, then inspect the path that exhausted or crossed its boundary. Do not treat the feature…
Pair timerlat’s IRQ and thread observations for the same CPU and activation before deciding where wakeup delay accumulated. Both values are measured from the intended timer expiry. Adding them double-counts the early delay; subtracting unrelated maxima creates a number that may never have occurred. This procedure uses upstream Linux and rtla sources at v6.12. It…
Use osnoise to classify interruptions of a per-CPU measurement loop, then investigate the dominant observed source with a focused trace. The result describes interference during that loop’s sampling window. It is not a direct measurement of every application’s lost execution time, and a large hardware-classified count is not automatically proof of faulty hardware. This workflow…
Use pressure stall information to ask how much time workloads lose to resource contention, then compare that loss with the application’s latency. A busy CPU can be doing useful work. A machine with apparently modest utilization can still have a particular workload stalled on memory or I/O. Utilization alone cannot distinguish those cases. This article…
DMA API debugging is a contract checker for the driver’s mapping lifecycle. Before interpreting a quiet log, verify that its bookkeeping is active, has capacity and can still print the errors you need. A successful device transfer does not prove that the corresponding map, synchronization and unmap calls obeyed the kernel API. This procedure targets…
Preserve the first AER record, PCIe topology and recovery sequence before treating the post-reset device state as the original failure. A link or function reset can change what later reads reveal. The first reporting component, the device affected by recovery and the physical source of the defect need not be the same thing. This guide…
Read an EDAC event as a hardware-reporting record with a severity, topology and observation boundary. Preserve the raw event and the controller’s available counters before deciding whether it points to one replaceable component, a broader platform problem or an unrelated application defect. The reference is upstream Linux v6.12’s EDAC subsystem and documented sysfs ABI. The…
Decode taint as accumulated boot context, then locate the earlier event that set each relevant flag. A tainted kernel is not automatically unusable, and a taint letter does not identify the cause of the current crash. It tells the investigator which prior conditions may affect interpretation or reproduction. This article is pinned to upstream Linux…
A hung-task warning calls for a wait-dependency investigation: what must happen before the blocked task can run, and who can make it happen? It is not automatically a CPU lockup. Other tasks and interrupts may continue while one thread waits indefinitely for a resource, completion or lower-layer operation. This guide uses upstream Linux v6.12 hung-task…