Date: Fri, 3 Feb 2017 22:27:30 -0800 From: Jason Harmening <jason.harmening@gmail.com> To: 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: <CAM=8qa=YB_kBsFRS%2Ba7kR%2BZTkyjmRnwY7r9vfZ48SyyZ2BZddg@mail.gmail.com> In-Reply-To: <8523aaa5-6c30-9f9f-40f0-fdf82cdf1669@pix.net> 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>
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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. On Fri, Feb 3, 2017 at 9:54 PM, Kurt Lidl <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>> 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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