Date: Sat, 4 Feb 2017 10:25:29 +0100 From: Andreas Tobler <andreast@FreeBSD.org> To: Jason Harmening <jason.harmening@gmail.com>, Kurt Lidl <lidl@pix.net> Cc: Alexander Kabaev <kabaev@gmail.com>, "Jason A. Harmening" <jah@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org, Ed Maste <emaste@freebsd.org> Subject: Re: svn commit: r313037 - in head/sys: amd64/include kern mips/include net powerpc/include sparc64/include Message-ID: <6bf86e46-9714-c7e9-8d47-845761e2de24@FreeBSD.org> In-Reply-To: <CAM=8qa=YB_kBsFRS%2Ba7kR%2BZTkyjmRnwY7r9vfZ48SyyZ2BZddg@mail.gmail.com> References: <201702010332.v113WnYf041362@repo.freebsd.org> <20170203231238.0675c289@kan> <CAM=8qa=h3=sfro02hCQyzqkDnLO7TnQJ8ugCoa5=MfNE_OCgZg@mail.gmail.com> <8523aaa5-6c30-9f9f-40f0-fdf82cdf1669@pix.net> <CAM=8qa=YB_kBsFRS%2Ba7kR%2BZTkyjmRnwY7r9vfZ48SyyZ2BZddg@mail.gmail.com>
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On 04.02.17 07:27, Jason Harmening wrote: > It's hard to argue with that:) I've backed it out until we can figure > out what's going on. > Sorry for the breakage. For the record, powerpc64 was also affected. Andreas > > On Fri, Feb 3, 2017 at 9:54 PM, Kurt Lidl <lidl@pix.net > <mailto:lidl@pix.net>> wrote: > > Having just spent a couple of hours bisecting what broke the kernel on > my mips64 machine, I can definitively state it was this commit. > > With this commit in place, the kernel hangs early in the > autoconfiguration: > > gcc version 4.2.1 20070831 patched [FreeBSD] > Preloaded elf kernel "kernel" at 0xffffffff80aa96a0. > real memory = 523239424 (510976K bytes) > Physical memory chunk(s): > 0x00bf3000 - 0x080d5fff, 122564608 bytes (29923 pages) > 0x08101000 - 0x0ff00fff, 132120576 bytes (32256 pages) > 0x410000000 - 0x41f196fff, 253325312 bytes (61847 pages) > avail memory = 504360960 (480MB) > Create COP2 context zone > AP #1 started! > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs > ---- hangs here ---- > > -Kurt > > On 2/4/17 12:29 AM, Jason Harmening wrote: > > Hi, > > I'm a bit confused as to how this change breaks MIPS. The new > function, > get_pcpu() is intended to be used only to access the per-cpu data > pointer locally. It returns pcpup, which is the per-cpu pointer > wired > into the local TLB to translate to the local CPU's physical data > region, > correct? > > This is the same value used by the per-CPU accessors such as > PCPU_ADD > and PCPU_GET. The MI portions of this change only use get_pcpu() to > access the local CPU's data, e.g. under a critical section in the > rmlock. It is not intended to be used for iterating all CPUs. > > If I've missed something and MIPS is truly broken by this, then I'll > gladly revert, but (maybe because it's late) I'm not seeing > where this > goes wrong on MIPS. > > Thanks, > Jason > > On Fri, Feb 3, 2017 at 8:12 PM, Alexander Kabaev > <kabaev@gmail.com <mailto:kabaev@gmail.com> > <mailto:kabaev@gmail.com <mailto:kabaev@gmail.com>>> wrote: > > On Wed, 1 Feb 2017 03:32:49 +0000 (UTC) > "Jason A. Harmening" <jah@FreeBSD.org> wrote: > > > Author: jah > > Date: Wed Feb 1 03:32:49 2017 > > New Revision: 313037 > > URL: https://svnweb.freebsd.org/changeset/base/313037 > <https://svnweb.freebsd.org/changeset/base/313037>; > <https://svnweb.freebsd.org/changeset/base/313037 > <https://svnweb.freebsd.org/changeset/base/313037>>; > > > > Log: > > Implement get_pcpu() for the remaining architectures and > use it to > > replace pcpu_find(curcpu) in MI code. > > > > Modified: > > head/sys/amd64/include/pcpu.h > > head/sys/kern/kern_rmlock.c > > head/sys/mips/include/pcpu.h > > head/sys/net/netisr.c > > head/sys/powerpc/include/cpufunc.h > > head/sys/powerpc/include/pcpu.h > > head/sys/sparc64/include/pcpu.h > > > > Hi, > > this change was not reviewed nor testing was thought for all > architectures it touches. The change happens to break MIPS quite > thoroughly, since MIPS is using different pointers when > accessing PCPU > area locally and when doing iterations using cpu_to_cpuid > array. I > therefore officially am requesting this change to be > reverted until > reasonable solution is found to unbreak architectures that > use wired > TLBs to access local per-CPU data. > > -- > Alexander Kabaev > > > >
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