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Date: Mon, 5 Jan 2009 18:21:36 -0800 From: "john stultz-lkml" <johnstul.lkml@...il.com> To: "Chris Adams" <cmadams@...aay.net> Cc: "Linas Vepstas" <linasvepstas@...il.com>, linux-kernel@...r.kernel.org, "Thomas Gleixner" <tglx@...utronix.de> Subject: Re: Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009 On Fri, Jan 2, 2009 at 4:21 PM, Chris Adams <cmadams@...aay.net> wrote: > Once upon a time, Linas Vepstas <linasvepstas@...il.com> said: >> Below follows a summary of the reported crashes. I'm ignoring the >> zillions of "mine didn't crash" reports, or the "you're a paranoid >> conspiracy theorist, its random chance" reports. > > I have reproduced this and got a stack trace (this is with Fedora 8 and > kernel kernel-2.6.26.6-49.fc8.x86_64): > [snip] > Basically (to my untrained eye), the leap second code is called from the > timer interrupt handler, which holds xtime_lock. The leap second code > does a printk to notify about the leap second. The printk code tries to > wake up klogd (I assume to prioritize kernel messages), and (under some > conditions), the scheduler attempts to get the current time, which tries > to get xtime_lock => deadlock. This analysis looks correct to me. Grrrr. This has bit us a few times since the "no printk while holding the xtime lock" restriction was added. Thomas: Do you think this warrents adding a check to the printk path to make sure the xtime lock isn't held? This way we can at least get a warning when someone accidentally adds a printk or calls a function that does while holding the xtime_lock. thanks -john -- 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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