On Fri, May 15, 2020 at 5:10 PM Thomas Gleixner <[email protected]> wrote: > > > The scheduler IPI does not need the full interrupt entry handling logic > when the entry is from kernel mode. > > Even if tracing is enabled the only requirement is that RCU is watching and > preempt_count has the hardirq bit on. > > The NOHZ tick state does not have to be adjusted. If the tick is not > running then the CPU is in idle and the idle exit will restore the > tick. Softinterrupts are not raised here, so handling them on return is not > required either. > > User mode entry must go through the regular entry path as it will invoke > the scheduler on return so context tracking needs to be in the correct > state. > > Use IDTENTRY_RAW and the RCU conditional variants of idtentry_enter/exit() > to guarantee that RCU is watching even if the IPI hits a RCU idle section. > > Remove the tracepoint static key conditional which is incomplete > vs. tracing anyway because e.g. ack_APIC_irq() calls out into > instrumentable code. > > Avoid the overhead of irq time accounting and introduce variants of > __irq_enter/exit() so instrumentation observes the correct preempt count > state.
Leftover text from an old version? The code is Reviewed-by: Andy Lutomirski <[email protected]>
