On Fri, 10 Apr 2015 14:36:34 +0200 Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > Subject: [PATCH] kernel/irq_work: fix no_hz deadlock > > Invoking NO_HZ's irq_work callback from timer irq is not working very > well if the callback decides to invoke hrtimer_cancel(): > > |hrtimer_try_to_cancel+0x55/0x5f > |hrtimer_cancel+0x16/0x28 > |tick_nohz_restart+0x17/0x72 > |__tick_nohz_full_check+0x8e/0x93 > |nohz_full_kick_work_func+0xe/0x10 > |irq_work_run_list+0x39/0x57 > |irq_work_tick+0x60/0x67 > |update_process_times+0x57/0x67 > |tick_sched_handle+0x4a/0x59 > |tick_sched_timer+0x3b/0x64 > |__run_hrtimer+0x7a/0x149 > |hrtimer_interrupt+0x1cc/0x2c5 > > and here we deadlock while waiting for the lock which we are holding. > To fix this I'm doing the same thing that upstream is doing: is the > irq_work dedicated IRQ and use it only for what is marked as "hirq" > which should only be the FULL_NO_HZ related work. I'm backporting this to the stable releases, and I'm a bit worried about the above comment. The new Scheduler IPI code uses work queues and requires it to be done in a hard irq. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
