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Message-ID: <20140718225005.GA17140@amos.fritz.box> Date: Sat, 19 Jul 2014 00:50:05 +0200 From: Andreas Bombe <aeb@...ian.org> To: Jan Kara <jack@...e.cz> Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [REGRESSION] Boot hang with 939f04bec printk: enable interrupts before calling console_trylock_for_printk() On Thu, Jul 17, 2014 at 10:31:37AM +0200, Jan Kara wrote: > On Wed 16-07-14 23:34:08, Andreas Bombe wrote: > > On Mon, Jul 14, 2014 at 10:35:27AM +0200, Jan Kara wrote: > > > On Sun 29-06-14 00:50:50, Andreas Bombe wrote: > > > > None of the post 3.15 kernel boot for me. They all hang at the GRUB > > > > screen telling me it loaded and started the kernel, but the kernel > > > > itself stops before it prints anything (or even replaces the GRUB > > > > background graphics). > > > > > > > > I bisected it down to 939f04bec1a4ef6ba4370b0f34b01decc844b1b1 "printk: > > > > enable interrupts before calling console_trylock_for_printk()". > > > > Reverting that patch on the latest kernel (git 24b414d5a7) allows me to > > > > boot normally. I fixed the conflict in the revert by leaving in the "if > > > > (in_sched) return printed_len;". > > > > > > > > I have the "early printk via the EFI framebuffer" option enabled, > > > > disabling it made no difference however. > > > Thanks for report. I've been on vacation so I'm replying with a delay. I > > > believe this is one of the issues where this patch just uncovers underlying > > > problem - I belive lockdep tries to report some locking issue in console > > > driver code (this patch increased lockdep coverage of console driver code) > > > however we are holding some locks in printk code which make lockdep > > > deadlock. Can you try running with the attached patch? > > > > EUNABLE > > > > You forgot to attach a patch. > Bah, sorry. Attaching now. I don't see anything in /sys/kernel/debug/tracing/trace_pipe or .../trace (besides the header) with your patch applied. In case you meant to test it with the problematic printk change, I also tried with the revert reverted. That still hangs as before without any error report to see. I checked the kernel logs and there is also no lockdep report anywhere. I get the "trace_printk() being used" notice but nothing else of interest around there. Though the notice should mean trace_printk() was used at least once? -- 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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