On Wed, 8 Nov 2023 11:15:37 -0800 Kees Cook <keescook@xxxxxxxxxxxx> wrote: > FOr the memcpy_kunit.c cases, I don't think there are preemption > locations in its loops. Perhaps I'm misunderstanding something? Why will > the memcpy test no longer produce softlockup splats? This patchset will switch over to a NEED_RESCHED_LAZY routine, so that VOLUNTARY and NONE preemption models will be forced to preempt if its in the kernel for too long. Time slice is over: set NEED_RESCHED_LAZY For VOLUNTARY and NONE, NEED_RESCHED_LAZY will not preempt the kernel (but will preempt user space). If in the kernel for over 1 tick (1ms for 1000Hz, 4ms for 250Hz, etc), if NEED_RESCHED_LAZY is still set after one tick, then set NEED_RESCHED. NEED_RESCHED will now schedule in the kernel once it is able to regardless of preemption model. (PREEMPT_NONE will now use preempt_disable()). This allows us to get rid of all cond_resched()s throughout the kernel as this will be the new mechanism to keep from running inside the kernel for too long. The watchdog is always longer than one tick. -- Steve
