From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 18 Apr 2008 09:37:32 +0200 From: Ingo Molnar Subject: Re: 2.6.25-mm1: not looking good Message-ID: <20080418073732.GA22724@elte.hu> References: <20080417160331.b4729f0c.akpm@linux-foundation.org> <20080417164034.e406ef53.akpm@linux-foundation.org> <20080417171413.6f8458e4.akpm@linux-foundation.org> <48080FE7.1070400@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48080FE7.1070400@windriver.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Jason Wessel Cc: Andrew Morton , tglx@linutronix.de, penberg@cs.helsinki.fi, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jmorris@namei.org, sds@tycho.nsa.gov List-ID: * Jason Wessel wrote: > > [...] The final initcall is init_kgdbts() and disabling KGDB > > prevents the hang. > That enables verbose logging of exactly what is going on and will show > where wheels fall off the cart. If the kernel is dying silently it > means the early exception code has completely failed in some way on > the kernel architecture that was selected, and of course the .config > is always useful in this case. incidentally, just today, in overnight testing i triggered a similar hang in the KGDB self-test: http://redhat.com/~mingo/misc/config-Thu_Apr_17_23_46_36_CEST_2008.bad to get a similar tree to the one i tested, pick up sched-devel/latest from: http://people.redhat.com/mingo/sched-devel.git/README pick up that failing .config, do 'make oldconfig' and accept all the defaults to get a comparable kernel to mine. (kgdb is embedded in sched-devel.git.) the hang was at: [ 12.504057] Calling initcall 0xffffffff80b800c1: init_kgdbts+0x0/0x1b() [ 12.511298] kgdb: Registered I/O driver kgdbts. [ 12.515062] kgdbts:RUN plant and detach test [ 12.520283] kgdbts:RUN sw breakpoint test [ 12.524651] kgdbts:RUN bad memory access test [ 12.529052] kgdbts:RUN singlestep breakpoint test full log: http://redhat.com/~mingo/misc/log-Thu_Apr_17_23_46_36_CEST_2008.bad note that this was a 64-bit config too - our tests do a perfect mix of 50% 32-bit and 50% 64-bit kernels. So single-stepping of the kernel broke in some circumstances. find the boot log below. (it also includes all command line parameters) This is the first time ever i saw the self-test in KGDB hanging, so it's some recent non-KGDB change that provoked it or made it more likely. The KGDB self-test runs very frequently in my bootup tests: [ 12.508236] kgdb: Registered I/O driver kgdbts. [ 12.511245] kgdbts:RUN plant and detach test [ 12.517418] kgdbts:RUN sw breakpoint test [ 12.521056] kgdbts:RUN bad memory access test [ 12.525515] kgdbts:RUN singlestep breakpoint test [ 12.531483] kgdbts:RUN hw breakpoint test [ 12.536142] kgdbts:RUN hw write breakpoint test [ 12.541007] kgdbts:RUN access write breakpoint test [ 12.546223] kgdbts:RUN do_fork for 100 breakpoints so the latest kgdb-light tree literally survived thousands of such tests since it was changed last. unfortunately, the condition was not reproducible - i booted it once more and then it came up just fine - using the same bzImage. there's no recent change in x86.git related to the TF flag that i could think of to cause something like this. I checked changes to traps_64.c and entry_64.S, and nothing suspicious. Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org