Re: Question about kthread_mod_delayed_work() allowed context
From: Petr Mladek <pmladek@suse.com>
Date: 2020-02-13 08:33:37
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linux-rt-users, lkml, netdev
On Wed 2020-02-12 21:17:53, Grygorii Strashko wrote:
On 12/02/2020 17:41, Petr Mladek wrote:quoted
On Tue 2020-02-11 12:23:59, Grygorii Strashko wrote:quoted
Hi All, I'd like to ask question about allowed calling context for kthread_mod_delayed_work(). The comment to kthread_mod_delayed_work() says: * This function is safe to call from any context including IRQ handler. * See __kthread_cancel_work() and kthread_delayed_work_timer_fn() * for details. */ But it has del_timer_sync() inside which seems can't be called from hard_irq context: kthread_mod_delayed_work() |-__kthread_cancel_work() |- del_timer_sync() |- WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));It is safe because kthread_delayed_work_timer_fn() is IRQ safe. Note that it uses raw_spin_lock_irqsave(). It is the reason why the timer could have set TIMER_IRQSAFE flag, see KTHREAD_DELAYED_WORK_INIT(). In more details. The timer is either canceled before the callback is called. Or it waits for the callback but the callback is safe because it can't sleep.I think, my issue (warning) could be related to the fact that kthread_init_delayed_work() is used, which seems doesn't set TIMER_IRQSAFE flag.
Great catch! It is a bug. Would you like to send the fix for kthread_init_delayed_work() or would you prefer me doing so? Best Regards, Petr _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel