sched,livepatch: Untangle cond_resched() and live-patching

2025-05-14T11:16:24+00:00

With the goal of deprecating / removing VOLUNTARY preempt, live-patch needs to stop relying on cond_resched() to make forward progress. Instead, rely on schedule() with TASK_FREEZABLE set. Just like live-patching, the freezer needs to be able to stop tasks in a safe / known state. [bigeasy: use likely() in __klp_sched_try_switch() and update comments] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Reviewed-by: Petr Mladek Tested-by: Petr Mladek Tested-by: Miroslav Benes Acked-by: Miroslav Benes Acked-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20250509113659.wkP_HJ5z@linutronix.de

livepatch,sched: Add livepatch task switching to cond_resched()

2023-03-22T16:09:28+00:00

There have been reports [1][2] of live patches failing to complete within a reasonable amount of time due to CPU-bound kthreads. Fix it by patching tasks in cond_resched(). There are four different flavors of cond_resched(), depending on the kernel configuration. Hook into all of them. A more elegant solution might be to use a preempt notifier. However, non-ORC unwinders can't unwind a preempted task reliably. [1] https://lore.kernel.org/lkml/20220507174628.2086373-1-song@kernel.org/ [2] https://lkml.kernel.org/lkml/20230120-vhost-klp-switching-v1-0-7c2b65519c43@kernel.org Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Petr Mladek Tested-by: Seth Forshee (DigitalOcean) Link: https://lore.kernel.org/r/4ae981466b7814ec221014fc2554b2f86f3fb70b.1677257135.git.jpoimboe@kernel.org

kernel/linux.git/include/linux/livepatch_sched.h, branch v6.19.11

sched,livepatch: Untangle cond_resched() and live-patching

livepatch,sched: Add livepatch task switching to cond_resched()