Date: Sat, 4 Feb 2017 00:54:15 -0500 From: Kurt Lidl <lidl@pix.net> To: Jason Harmening <jason.harmening@gmail.com>, Alexander Kabaev <kabaev@gmail.com> Cc: "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: <8523aaa5-6c30-9f9f-40f0-fdf82cdf1669@pix.net> In-Reply-To: <CAM=8qa=h3=sfro02hCQyzqkDnLO7TnQJ8ugCoa5=MfNE_OCgZg@mail.gmail.com> References: <201702010332.v113WnYf041362@repo.freebsd.org> <20170203231238.0675c289@kan> <CAM=8qa=h3=sfro02hCQyzqkDnLO7TnQJ8ugCoa5=MfNE_OCgZg@mail.gmail.com>
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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>> 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>; > > > > 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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