CVE-2025-21694: Undefined Security Weakness

In the Linux kernel, the following vulnerability has been resolved:

fs/proc: fix softlockup in __read_vmcore (part 2)

Since commit 5cbcb62dddf5 ("fs/proc: fix softlockup in __read_vmcore") the number of softlockups in __read_vmcore at kdump time have gone down, but they still happen sometimes.

In a memory constrained environment like the kdump image, a softlockup is not just a harmless message, but it can interfere with things like RCU freeing memory, causing the crashdump to get stuck.

The second loop in __read_vmcore has a lot more opportunities for natural sleep points, like scheduling out while waiting for a data write to happen, but apparently that is not always enough.

Add a cond_resched() to the second loop in __read_vmcore to (hopefully) get rid of the softlockups.