Messages in this thread | | | Subject | Re: [2.6.33-rc5] starting emacs makes lockdep warning | From | (Eric W. Biederman) | Date | Mon, 25 Jan 2010 22:17:15 -0800 |
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KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> writes:
>> > On Tue, Jan 26, 2010 at 11:20 AM, KOSAKI Motohiro >> > <kosaki.motohiro@jp.fujitsu.com> wrote: >> > > Hi >> > > >> > > Current linus tree made following lockdep warning when starting emacs command. >> > > Is this known issue? >> > > >> > > >> > > ========================================================= >> > > [ INFO: possible irq lock inversion dependency detected ] >> > > 2.6.33-rc5 #77 >> > > --------------------------------------------------------- >> > > emacs/1609 just changed the state of lock: >> > > (&(&tty->ctrl_lock)->rlock){+.....}, at: [<ffffffff8127c648>] tty_fasync+0xe8/0x190 >> > > but this lock took another, HARDIRQ-unsafe lock in the past: >> > > (&(&sighand->siglock)->rlock){-.....} >> > > >> > > and interrupts could create inverse lock ordering between them. >> > > >> > > >> > >> > Hey, >> > >> > does reverting commit 703625118 help? >> >> Seems solved. >> >> Thanks. > > I'm sorry. > I forgot to cc related person at last mail. > > Greg, can you please consider revert commit 703625118?
It looks like f_modown needs to do irqsave irqrestore to be safely called in this context. My apologies for missing this when I originally made the suggestion.
As for the other comments I would be very surprised if lock_kernel() offers any real protection.
I really don't understand what it is talking about siglock being irq unsafe, that seems wrong on oh so many levels.
Eric
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