Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [Critical] The clock event timer interrupt (HVMSG_TIMER_EXPIRED) is incorrectly processed in a kthread on PREEMPT_RT, violating the architectural requirement that the system tick must run in hardirq context. -- --- Patch [1]: [PATCH v2 1/2] Drivers: hv: vmbus: Replace lockdep_hardirq_threaded() with lockdep annotation --- commit f939a4b9727e456e689d5d7488e6095b1358e5b5 Author: Sebastian Andrzej Siewior <[email protected]> Drivers: hv: vmbus: Replace lockdep_hardirq_threaded() with lockdep annotation This commit replaces the use of lockdep_hardirq_threaded() with a lockdep annotation. This limits the threaded context on PREEMPT_RT to __vmbus_isr() and clarifies that the ISR is not a shared handler. > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c > index 23206640c6139..44877664d9d08 100644 > --- a/drivers/hv/vmbus_drv.c > +++ b/drivers/hv/vmbus_drv.c > @@ -1384,8 +1384,19 @@ void vmbus_isr(void) > if (IS_ENABLED(CONFIG_PREEMPT_RT)) { > vmbus_irqd_wake(); [Severity: Critical] This isn't a bug introduced by this patch, but is it safe to defer all VMbus interrupt processing to the vmbus_irqd kthread on PREEMPT_RT? When booting a PREEMPT_RT kernel on a Hyper-V host using legacy timer mode, the kthread handles the hypervisor timer message and invokes the timer ISR: vmbus_message_sched() if (msg->header.message_type == HVMSG_TIMER_EXPIRED) { hv_stimer0_isr(); This executes the clock event handler in thread context, which breaks the requirement that the system tick must run in hardirq context: hv_stimer0_isr() ce = this_cpu_ptr(hv_clock_event); ce->event_handler(ce); Because get_irq_regs() returns NULL when called from a kthread, calling tick_handle_periodic() and then update_process_times(user_mode(get_irq_regs())) will dereference a NULL pointer and panic the kernel. Alternatively, if high-resolution timers are used, tick_nohz_handler() sees a NULL regs pointer and skips tick_sched_handle(), completely stalling the scheduler tick and RCU updates, freezing the system. > } else { > - lockdep_hardirq_threaded(); > + static DEFINE_WAIT_OVERRIDE_MAP(vmbus_map, LD_WAIT_CONFIG); > + > + /* > + * vmbus_isr is never force-threaded and always invoked at hard [ ... ] -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
