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From: Nick Desaulniers <ndesaulniers@google.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>, Borislav Petkov <bp@alien8.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	x86@kernel.org, llvm@lists.linux.dev,
	linux-sparse@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel test robot <lkp@intel.com>,
	Nathan Chancellor <nathan@kernel.org>,
	linux-toolchains@vger.kernel.org
Subject: Re: [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__
Date: Mon, 24 Jan 2022 15:38:38 -0800	[thread overview]
Message-ID: <CAKwvOdm+pnKb2PU7H5W1ks8eFd3DPEtN5kzjhnz5TLLwpBLOsA@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOdmLzwz=02ypt0_1324_5-7i3Az7HizFaDMqZv__-D99uA@mail.gmail.com>

On Mon, Jan 24, 2022 at 3:26 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Jan 18, 2022 at 3:01 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > Apparently this patch isn't going to work after all :-(
> >
> >   https://lkml.kernel.org/r/202201190632.lhlaiCBk-lkp@intel.com
>
> I noticed in that report and
> https://lore.kernel.org/lkml/202201190702.XNSXrMTK-lkp@intel.com/
> that gcc-9 was used.  I wonder if %= has been fixed in gcc-10+? Have
> there been other reports with gcc-10+ for my patch?
>
> Boris' case of xfrm_output_resume is yet a third case; Boris, what
> version of gcc did you spot that with?
>
> If this is fixed in gcc-10, then we can probably add a comment with a
> FIXME link to the issue or commit to replace __COUNTER__ with %= one
> day.  If not, then we can probably come up with a reduced test case
> for the GCC devs to take a look at, then add the FIXME comment to
> kernel sources.


$ wget https://download.01.org/0day-ci/archive/20220119/202201190702.XNSXrMTK-lkp@intel.com/config
-O .config
$ make -j72 -s olddefconfig drivers/net/wireless/mac80211_hwsim.o
drivers/net/wireless/mac80211_hwsim.o: warning: objtool:
mac80211_hwsim_tx()+0x9aa: unreachable instruction
$ gcc --version
gcc (Debian 11.2.0-12) 11.2.0

:(

Let me see if I can come up with a reduced test case that I will
report upstream to https://gcc.gnu.org/bugzilla/.
-- 
Thanks,
~Nick Desaulniers

  reply	other threads:[~2022-01-25  4:48 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20220114010526.1776605-1-ndesaulniers@google.com>
     [not found] ` <YeQei0xNzMq7bFdg@zn.tnic>
     [not found]   ` <20220118192256.jzk5dnceeusq7x7u@treble>
     [not found]     ` <20220118230120.pivvson7qekfiqic@treble>
2022-01-24 23:26       ` [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__ Nick Desaulniers
2022-01-24 23:38         ` Nick Desaulniers [this message]
2022-01-25 18:49           ` Borislav Petkov
2022-01-25 23:31         ` Segher Boessenkool
2022-01-26  0:59           ` Nick Desaulniers
2022-01-26  2:12             ` Nick Desaulniers
2022-01-26 11:13               ` Segher Boessenkool
2022-01-31 20:45           ` Nick Desaulniers
2022-01-31 22:13             ` Segher Boessenkool

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