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Date: Mon, 20 Aug 2012 17:12:10 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Oleg Nesterov <oleg@...hat.com> Cc: Dave Jones <davej@...hat.com>, Linux Kernel <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, rostedt <rostedt@...dmis.org>, dhowells <dhowells@...hat.com>, Al Viro <viro@...iv.linux.org.uk> Subject: Re: lockdep trace from posix timers On Mon, 2012-08-20 at 17:05 +0200, Oleg Nesterov wrote: > On 08/20, Peter Zijlstra wrote: > > > > +static void __task_work_run(struct callback_head *tail) > > { > > - struct task_struct *task = current; > > - struct callback_head *p, *q; > > - > > - while (1) { > > - raw_spin_lock_irq(&task->pi_lock); > > - p = task->task_works; > > - task->task_works = NULL; > > - raw_spin_unlock_irq(&task->pi_lock); > > - > > - if (unlikely(!p)) > > - return; > > - > > - q = p->next; /* head */ > > - p->next = NULL; /* cut it */ > > - while (q) { > > - p = q->next; > > - q->func(q); > > - q = p; > > + struct callback_head **head = ¤t->task_works; > > + > > + do { > > + struct callback_head *work = xchg(head, NULL); > > + while (work) { > > + struct callback_head *next = ACCESS_ONCE(work->next); > > + > > + WARN_ON_ONCE(work == &dead); > > + > > + work->func(work); > > + work = next; > > } > > - } > > + } while (cmpxchg(head, NULL, tail) != NULL); > > Yes, we can add the explicit argument to __task_work_run(), but it can > check PF_EXITING instead, this looks simpler to me. I guess we could.. but I thought the explicit callback was simpler ;-) > Note also your patch breaks fifo, but this is fixable. Why do you care about the order? Iterating a single linked queue in fifo seems more expensive than useful. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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