[PATCH] timer/migration: Remove buggy early return on deactivation [was Re: Unexplained long boot delays [Was Re: [GIT PULL] RCU changes for v6.9]]

[Frederic Weisbecker]

On Thu, Mar 14, 2024 at 03:05:53PM -0700, Boqun Feng wrote:
> I notice CPU3 didn't have its own non-deferrable timer queued (local or
> global), so could the following happen?
> 
> 	timer_base_try_to_set_idle():
> 	  __get_next_timer_interrupt():
> 	    fetch_next_timer_interrupt():
> 	      // nextevt_local == nextevt_global == basej + NEXT_TIMER_MAX_DELTA
> 	      // tevt->local == tevt->gloabl = KTIME_MAX
> 	    timer_use_tmigr():
> 	      tmigr_cpu_deactivate():
> 	        __tmigr_cpu_deactivate():
> 		  // tmc->cpuevt.ignore untouched still == true
> 		  walk_groups(&tmigr_inactive_up, ...):
> 		    tmigr_inactive_up():
> 		      data->remote = true;
> 		      tmigr_update_events():
> 		        if (child) { // child is NULL
> 			  ...
> 			} else {
> 			  first_childevt = evt = data->evt;
> 
> 			  if (evt->ignore && !remote)
> 			    return true; // no remote tick is picked.
> 			  ...
> 			}

Nice catch! Florian can you try the following?