Excerpts from Peter Zijlstra's message of July 6, 2021 9:06 pm: > On Tue, Jul 06, 2021 at 12:18:07PM +0800, Huacai Chen wrote: >> + .align 5 /* 32 byte rollback region */ >> +SYM_FUNC_START(__arch_cpu_idle) >> + /* start of rollback region */ >> + LONG_L t0, tp, TI_FLAGS >> + nop >> + andi t0, t0, _TIF_NEED_RESCHED >> + bnez t0, 1f >> + nop >> + nop >> + nop >> + idle 0 >> + /* end of rollback region */ >> +1: >> + jirl zero, ra, 0 >> +SYM_FUNC_END(__arch_cpu_idle) > >> +/* >> + * Common Vectored Interrupt >> + * Complete the register saves and invoke the do_vi() handler >> + */ >> +SYM_FUNC_START(except_vec_vi_handler) >> + la t1, __arch_cpu_idle >> + LONG_L t0, sp, PT_EPC >> + /* 32 byte rollback region */ >> + ori t0, t0, 0x1f >> + xori t0, t0, 0x1f >> + bne t0, t1, 1f >> + LONG_S t0, sp, PT_EPC > > Seriously, you're having your interrupt handler recover from the idle > race? On a *new* architecture? It's heavily derived from MIPS (does that make the wholesale replacement of arch/mips copyright headers a bit questionable?). I don't think it's such a bad trick though -- restartable sequences before they were cool. It can let you save an irq disable in some cases (depending on the arch of course). Thanks, Nick
