Messages in this thread | | | Subject | Re: [GIT PULL] printk: Support for full dynticks mode | From | Steven Rostedt <> | Date | Mon, 04 Feb 2013 21:42:02 -0500 |
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On Mon, 2013-02-04 at 18:09 -0800, Andrew Morton wrote:
> I don't think so. Conceptually printk() should be "inner" to the > scheduler and shouldn't call into sched things at all. The (afaik > sole) exception to that was the klogd wakeup. > > Traditionally the deadlock happened when calling printk() with > tasklist_lock (now q->lock) held. printk() would call wake_up(klogd) > and wake_up() tries to take tasklist_lock and boom. Moving the > wake_up() out to the tick "thread" fixed that. > > Maybe there were other deadlock scenarios, dunno. That knowledge > appears to be disappearing into the mists of time :(
Even without the printk irq_work the current printk method uses a delayed wakeup anyway.
The wake_up_klogd() sets PRINTK_PENDING_WAKEUP, and the wakeup happens at time of the tick. I don't see where there is a deadlock. I added a printk in __sched_setscheduler() where the run queue lock is held, and booted that with full lockdep debugging enabled. No deadlock is detected.
Do we really even need that printk_sched()?
-- Steve
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