Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Content-Type: text/plain;
        charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.500.231\))
Subject: Re: [PATCH v2 2/3] compiler: inline does not imply notrace
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20230525222844.6a0d84f8@rorschach.local.home>
Date:   Thu, 25 May 2023 22:17:33 -0700
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-arm-kernel@lists.infradead.org,
        LKML <linux-kernel@vger.kernel.org>, linux-ia64@vger.kernel.org,
        linux-um@lists.infradead.org,
        Linux-Arch <linux-arch@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>, Andy Lutomirski <luto@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Borislav Petkov <bp@alien8.de>, X86 ML <x86@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <D4B1FB24-C351-411B-8A40-4DAFE95FA921@gmail.com>
References: <20230525210040.3637-1-namit@vmware.com>
 <20230525210040.3637-3-namit@vmware.com>
 <20230525222844.6a0d84f8@rorschach.local.home>
To:     Steven Rostedt <rostedt@goodmis.org>
Precedence: bulk


> On May 25, 2023, at 7:28 PM, Steven Rostedt <rostedt@goodmis.org> =
wrote:
>=20
> On Thu, 25 May 2023 14:00:39 -0700
> Nadav Amit <nadav.amit@gmail.com> wrote:
>=20
>> From: Nadav Amit <namit@vmware.com>
>>=20
>> Functions that are marked as "inline" are currently also not =
tracable.
>> This limits tracing functionality for many functions for no reason.
>> Apparently, this has been done for two reasons.
>>=20
>> First, as described in commit 5963e317b1e9d2a ("ftrace/x86: Do not
>> change stacks in DEBUG when calling lockdep"), it was intended to
>> prevent some functions that cannot be traced from being traced as =
these
>> functions were marked as inline (among others).
>>=20
>> Yet, this change has been done a decade ago, and according to Steven
>> Rostedt, ftrace should have improved and hopefully resolved nested
>> tracing issues by now. Arguably, if functions that should be traced -
>> for instance since they are used during tracing - still exist, they
>> should be marked as notrace explicitly.
>>=20
>> The second reason, which Steven raised, is that attaching "notrace" =
to
>> "inline" prevented tracing differences between different configs, =
which
>> caused various problem. This consideration is not very strong, and =
tying
>> "inline" and "notrace" does not seem very beneficial. The "inline"
>> keyword is just a hint, and many functions are currently not tracable
>> due to this reason.
>>=20
>> Disconnect "inline" from "notrace".
>=20
> FYI, I have a patch queued (still needs to go through testing) that
> already does this ;-)
>=20
> =
https://lore.kernel.org/all/20230502164102.1a51cdb4@gandalf.local.home/

Ugh. If you cc=E2=80=99d me, I wouldn=E2=80=99t bother you during your =
vacation. :)

I think you may like the first patch in my series to precede this patch
though as some of the function I marked as =E2=80=9Cnotrace" are =
currently =E2=80=9Cinline=E2=80=9D.

Let me know how you want to proceed, so I would know how to break this
series.