Hi everybody,
I have been getting DPC watchdog timeouts every now and then and I really need to fix that.
I have benchmarked my DPC routine with KeQueryPerformanceCounter(NULL) around everything and it seemed that I am holding a lock for too long.
Ok, so I put all the processing code into its own driver thread and signal from the DPC via semaphores what task needs to be processed, which is then performed in the thread outside the DPC.
I call KeReleaseSemaphore for all the different items and left the benchmarking in there around each call.
It’s all working pretty well, but quite often I get a time period of ~100us between two KeReleaseSemphore calls which is obviously way too much for not doing anything but calling KeReleaseSemaphore.
Should I not be using semaphores for this kind of thing?
In some other thread I saw that someone was actually having issues with the DMA (PutScatterGatherList) which was unrelated to their DPC but hanging the CPU for too long and triggered a DPC timeout bugcheck pointing to their DPC and nothing to do with DMA.
I am processing the DMA interrupts the same way (a separate thread); the thread waits for a semaphore being released in the DPC. Also working really well usually.
Their workaround was to move from DMA Adapter v2 to v3, but I am using KMDF (v1.11) and don’t even know which DMA adapter version that creates for me. Not even sure if that’s a possibility for my DPC timeouts.
Any pointers would be much appreciated, thanks.