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From: Masahiro Yamada <masahiroy@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Anders Roxell <anders.roxell@linaro.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	"David S. Miller" <davem@davemloft.net>,
	Haren Myneni <haren@us.ibm.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Jiri Kosina <jikos@kernel.org>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Miroslav Benes <mbenes@suse.cz>, Petr Mladek <pmladek@suse.com>,
	Tal Gilboa <talgi@mellanox.com>,
	kunit-dev@googlegroups.com,
	Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	live-patching@vger.kernel.org
Subject: Re: [PATCH v2 2/2] kbuild: trace functions in subdirectories of lib/
Date: Wed, 22 Jul 2020 11:08:51 +0900
Message-ID: <CAK7LNASdytWgqQWux1cyBrGJb_FvS7Ur5UqgHaA2Xf5cwfL85A@mail.gmail.com> (raw)
In-Reply-To: <20200707120212.7010fa4f@oasis.local.home>

On Wed, Jul 8, 2020 at 1:02 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Tue,  7 Jul 2020 18:21:17 +0900
> Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> >   ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> >
> > exists here in sub-directories of lib/ to keep the behavior of
> > commit 2464a609ded0 ("ftrace: do not trace library functions").
> >
> > Since that commit, not only the objects in lib/ but also the ones in
> > the sub-directories are excluded from ftrace (although the commit
> > description did not explicitly mention this).
> >
> > However, most of library functions in sub-directories are not so hot.
> > Re-add them to ftrace.
>
> I'm OK with this change, but note, it wasn't just the hot path that I
> disabled ftrace on lib for, but some of these calls are done very early
> at boot up. It may have been PowerPC that I was stumbling over. The
> issue is that they would call mcount before the kernel was mapped
> properly, and the system would crash.
>
> My PowerPC box no longer boots so I can't test this anymore. But a lot
> has changed since 2008, and all this may very well be OK.
>
> -- Steve


That's why I split this into two commits
so that we can do git-bisect and
revert the second one in case of a regression.

Anyway, we have some more time to test this in linux-next
(and somebody reports an issue, if any).


-- 
Best Regards
Masahiro Yamada

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-07  9:21 [PATCH v2 1/2] kbuild: introduce ccflags-remove-y and asflags-remove-y Masahiro Yamada
2020-07-07  9:21 ` [PATCH v2 2/2] kbuild: trace functions in subdirectories of lib/ Masahiro Yamada
2020-07-07 16:02   ` Steven Rostedt
2020-07-22  2:08     ` Masahiro Yamada [this message]
2020-07-22 20:49       ` Steven Rostedt
2020-07-08  6:52   ` Petr Mladek
2020-07-08  9:23     ` Petr Mladek
2020-07-22  2:10       ` Masahiro Yamada
2020-07-07 19:58 ` [PATCH v2 1/2] kbuild: introduce ccflags-remove-y and asflags-remove-y Brendan Higgins
2020-07-07 21:25 ` Anders Roxell

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