On Tue, Nov 07, 2017 at 02:13:04PM -0800, Vineet Gupta wrote: > In the more likely case of returning to kernel from perf interrupt, do a > fast path returning w/o bothering about CONFIG_PREEMPT etc I think this needs more explaining and certainly also deserves a code comment. Is the argument something along these lines? Assumes the interrupt will never set TIF_NEED_RESCHED; therefore no preemption is ever required on return from the interrupt. What do you (on ARC) do about irq_work ? > +ENTRY(handle_interrupt_pct) > + > + INTERRUPT_PROLOGUE irq > + > + IRQ_DISABLE > + > + lr r0, [ICAUSE] > + > + bl.d arch_do_IRQ > + mov r1, sp > + > + ld r0, [sp, PT_status32] ; returning to User/Kernel Mode > + btst r0, STATUS_U_BIT > + bnz resume_user_mode_begin > + > + clri > + b .Lisr_ret_fast_path_to_k > + > +END(handle_interrupt_pct)
