Messages in this thread | | | Subject | Re: [PATCH 08/10] posix-cpu-timers: Migrate to use new tick dependency mask model | From | Chris Metcalf <> | Date | Fri, 24 Jul 2015 12:57:24 -0400 |
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On 07/23/2015 12:42 PM, Frederic Weisbecker wrote: > +static void cpu_timer_list_dequeue(struct cpu_timer_list *t) > +{ > + if (!list_empty(&t->entry)) > + cpu_timer_dec_tick_dependency(); > + list_del_init(&t->entry); > +}
Is the list_empty() test necessary? It wasn't in the original posix-timers code, and it feels like a pretty serious bug if you're doing a list_del on an empty list.
At a higher level, is the posix-cpu-timers code here really providing the right semantics? It seems like before, the code was checking a struct task-specific state, and now you are setting a global state such that if ANY task anywhere in the system (even on housekeeping cores) has a pending posix cpu timer, then nothing can go into nohz_full mode.
Perhaps what is needed is a task_struct->tick_dependency to go along with the system-wide and per-cpu flag words? -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com
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