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Re: [PATCH] ARM: Blacklist GCC 4.8.0 to GCC 4.8.2 - PR58854 (fwd)

by Nicolas Pitre

FYI. The whole thread is available here: http://article.gmane.org/gmane.linux.ports.arm.omap/119412 ---------- Forwarded message ---------- Date: Thu, 16 Oct 2014 01:18:01 +0100 From: Russell King - ARM Linux <linux(a)arm.linux.org.uk> To: Peter Hurley <peter(a)hurleysoftware.com> Cc: Nathan Lynch <Nathan_Lynch(a)mentor.com>, David Laight <David.Laight(a)ACULAB.COM>, Otavio Salvador <otavio(a)ossystems.com.br>, Linus Torvalds <torvalds(a)linux-foundation.org>, Nicolas Pitre <nico(a)fluxnic.net>, Linux OMAP Mailing List <linux-omap(a)vger.kernel.org>, linux-arm-kernel(a)lists.infradead.org Message-ID: <20141016001801.GQ12379(a)n2100.arm.linux.org.uk> Subject: Re: [PATCH] ARM: Blacklist GCC 4.8.0 to GCC 4.8.2 - PR58854 On Wed, Oct 15, 2014 at 06:18:30PM -0400, Peter Hurley wrote: > On 10/15/2014 05:56 PM, Russell King wrote: > > I was in two minds whether to include 4.8.3 as Linaro released a buggy > > toolchain which identifies itself as 4.8.3, but I decided that's also > > a distro problem. IMHO Linaro should really think about taking that > > compiler down given the seriousness of this bug and it being > > indistinguishable from the fixed stock version. > > Maybe it's unfair to blame them; Linaro just took a snapshot and > released what was there. > > If gcc is going to retain the "change release number then add all the > new features" model, some kind of prerelease indicator would help > eliminate this kind of problem. And that indicator should be both > a preprocessor define and parseable from the command line :) My comment is not to attribute blame to them, my comment is entirely on a technical level. My reasoning is that the bug is just as prevalent in userspace, though it will occur less often. Any program which uses signal handlers is a candidate for exactly the same kind of corruption, since you can receive that signal between the point that the stack pointer is modified and the function loads the parent context. Of course, there are ways around that: don't use signal handlers, or if you do, use alternate signal stacks. Neither of those can be guaranteed for any program though. So, let me put this another way: a compiler with this bug is _completely_ unsuitable for use for compiling programs for use under the Linux kernel _as well_ as the Linux kernel itself. The difference is that the Linaro compilers come with an expectation that they are usable on ARM... whereas stock versions cover a lot more and so the ARM arch is probably very small number of their users. Hence why I recommend that Linaro takes down their buggy compiler. Their 4.8.3 version should not be used *anywhere*, just the same as the stock 4.8 to 4.8.2 inclusive should also not be used anywhere on ARM either.

11 years, 5 months

[ACTIVITY] Week 41

by Charles Baylis

== Progress == Neon vld/vst [4/10] . submitted v2 of vldN_lane patch (respin of patches 1&2 only) . continued ML discussion about patches 3&4. Tried out jenkins/cbuild infrastructure [1/10] . hardest part was getting git.linaro.org/people to hold my test tree . https://wiki.linaro.org/Platform/Systems/GitServer#Creating_new_repositories . if it doesn't work, ask ITS to check you are in the git-users group . still need to find where the results go. bug 403/418 wrong line number on neon error messages [2/10] . experimented with a couple of ways to solve this bug 715 [2/10] . investigated and closed as only affects deprecated old ABI Misc [1/10] == Plan == Benchmark 2014.10 release Continue bug 403/418 work

11 years, 5 months

[ACTIVITY] 6 - 10 October 2014

by Will Newton

== Progress == * Further work on malloc single-thread optimizations (2/10, TCWG-436) - Still pending some resolution on direction from upstream * Upstream work (1/10, CARD-341) - Patch review - Applied binutils patch for missing AArch64 relocs * Further work on malloc app benchmark framework (2/10, TCWG-441) - Found a possible way to get memory statistics without hacks, should improve speed and reliability of the benchmark framework * Email, meetings, etc. (1/10) * Thursday and Friday annual leave (4/10) == Issues == * None == Plan == * Get malloc app benchmark framework into shape and committed * Figure out direction for malloc single thread optimization work -- Will Newton Toolchain Working Group, Linaro

11 years, 5 months

[ACTIVITY] 6th - 10th October

by Bernie Ogden

cbuild2 benchmarking - TCWG-360 [7/10] * Fixed/worked around some especially resilient bugs ** Mostly relate to running benchmarks through LAVA, which may be less important in the near future * Wrote a doc * Upstreamed some code that works about as I want it to Meetings/mail/etc [3/10] =Plan= cbuild2 benchmarking * Work through TODO list from connect * Tidy up behaviour on shutdown * Storage issues * (Maybe) persuade a LAVA Juno to work for benchmarking or configure spec Hopefully pick up something else

11 years, 5 months

[ACTIVITY] Week 41

by Yvan Roux

== Issues == * None. == Progress == * GCC 4.9 2014.10 (6/10) - Completed remaining backports. - Looked at some regression (1 backport reverted) * TCWG 59 : Improve libunwind AArch64 support (1/10) - Reviewed AArch64 patch. * Misc: (3/10) - Various meetings. == Plan == * FSF branch merge and 2014.10 release.

11 years, 5 months

[ACTIVITY] 6 October 2014 to 10 October 2014.

by Venkataramanan Kumar

= Progress == * Core mark benchmark and report for PGO and PGO + LTO (4/10) More profiling and collected numbers and reported. JIRA card TCWG-181 updated. Adding LTO gains in x86 and degrades in Aarch64 . * Addressed machine bring up issues, debugged and installed necessary packages for both x86 and Aarch64 (1/10) * PR 62308 - Analyzed RTL dumps. Looks to be similar issue solved in trunk. Git bisected and found the passing revision in trunk. posted my comments. waiting for feedback. (2/10) * Misc [3/10] Internal work, emails, AMD meetings and 1-1 with inline manger. 1-1 with Maxim, christophe and 1-1 with ryan Linaro status call == Plan == * Coremark benchmark and profiling for PGO and PGO + LTO. Investigate LTO degradation causes and report. * Investigate PR 63173 * Setup Cbuildv2 build in internal machine. == Issues == Experiencing Hardware connection issues and kernel instability issues with my local machines.

11 years, 5 months

[ACTIVITY] 6-10 October 2014

by Kugan

== Holiday == * Public Holiday (2/10) * Leave (4/10) == Progress == * Zero/sign extension elimination with widening types (4/10) - Started experimented with a pass for widening type. - Verified for one simple test-case. - Bootstrapping is failing and looking into it. == Plan == * Continue with Zero/sign extension pass.

11 years, 5 months

[ACTIVITY] Week 41

by Renato Golin

== Progress == * Automation Framework (CARD-1378 1/10) - Planning LAVA server for new TCWG gateway * Buildbots (TCWG-76 7/10) - Fixing Compiler-RT buildbot (from 69 to 4 failures) * Background (2/10) - Code review, meetings, discussions, etc. - Re-testing a change in inst combine that broke bots before - Reviewing CMake builder for Windows builds - Discussing clang-reformat on lld's codebase == Plan == * Continue fixing the Compiler-RT buildbot * Present 2 talks at Linux Plumbers

11 years, 5 months

[ACTIVITY] 6-10 October 2014

by Christophe Lyon

== Progress == * GCC trunk/4.9 cross-validation (CARD-647) (2/10) - trunk build for aarch64 reported to fail because libsanitizer requires an update. Pinged libsanitizers maintainers but got no answer so far. - posted testsuite patch to test if -shared is supported - managed to find how to force target-dependent -mword-relocations flags to compile testglue, without needing a testuite patch :-) * Validation (3/10) - compared cbuild2 schroot-test branch using (default) shared libs and forcing static libs Using static libs causes many unresolved and unsupported tests - compared using unix.exp and arm-linux.exp: the latter causes creates instability in the results * Neon intrinsics tests (2/10) - rebased on trunk, applied requested changes - the make-check parallelization support has changed mid-September, took some time to discover that my .exp harness was now incompatible. * Misc (3/10) - calls/meetings == Next == * GCC trunk/4.9 cross-validation - continue investigation of abi_check test * Neon intrinsic tests update, trying to take float16 types into account * cbuild2: - compare results + validation time of stable and schroot-test branches - look at backport-test script + logs

11 years, 5 months

[ACTIVITY] 29th September - 3rd October

by Bernie Ogden

cbuild2 benchmarking - TCWG-360 [7/10] * Cleaned up and upstreamed some code that works * Fixed a couple of issues raised by LAVA people ** No longer scraping the logs ** No longer assuming stable IP addresses lowlevellock.h comments - CARD-341 [1/10] * Respun based on Carlos' comments Meetings/mail/etc - [2/10] =Plan= cbuild2 benchmarking * Upstream code-with-fixes * Write a doc * Invite people to start using this thing ** Assuming that the storage questions get resolved * Work through list of tweaks Get up to speed on glibc vector math thread

11 years, 5 months

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