Then she found it. The interrupt handler: rtl8169_interrupt . On a packet receive, the chip raises a line on the PCI bus. The kernel calls this routine. The routine reads a status register via MMIO. Then it does the dance: acknowledge the interrupt, schedule an NAPI poll, clear the bit.
The link came up. The drone's test pattern started: 10,000 packets per second, each with a sequence number. driver for pci device
- tp->intr_mask = RTL_EVENT_NAPI; + tp->intr_mask = RTL_EVENT_NAPI; + /* Ensure mask write is visible before re-enabling chip interrupts */ + wmb(); RTL_W32(tp, IntrMask, tp->intr_mask); She compiled the kernel module locally. make -C /lib/modules/$(uname -r)/build M=$(pwd) modules . sudo rmmod r8169 sudo insmod ./r8169.ko Then she found it
The terminal blinked, patient and green on black. Elara typed the incantation: The kernel calls this routine
Linus Torvalds would never know her name. But somewhere in the vast, humming machine of the Linux kernel, her fix would live. A single barrier. A whispered correction. The difference between a falling drone and a perfect harvest.