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Date:   Tue, 18 Apr 2023 15:25:33 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, Ben Segall <bsegall@google.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Mel Gorman <mgorman@suse.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Valentin Schneider <vschneid@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH RFC] preempt: Put preempt_enable() within an
 instrumentation*() section.
Message-ID: <20230418132533.GA4253@hirez.programming.kicks-ass.net>
References: <20230309072724.3F6zRkvw@linutronix.de>
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On Thu, Mar 09, 2023 at 08:27:24AM +0100, Sebastian Andrzej Siewior wrote:
> Callers of preempt_enable() can be within an noinstr section leading to:
> | vmlinux.o: warning: objtool: native_sched_clock+0x97: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
> | vmlinux.o: warning: objtool: kvm_clock_read+0x22: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
> | vmlinux.o: warning: objtool: local_clock+0xb4: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section
> | vmlinux.o: warning: objtool: enter_from_user_mode+0xea: call to preempt_schedule_thunk() leaves .noinstr.text section
> | vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0x140: call to preempt_schedule_thunk() leaves .noinstr.text section
> | vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xf2: call to preempt_schedule_thunk() leaves .noinstr.text section
> | vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xea: call to preempt_schedule_thunk() leaves .noinstr.text section
> 
> This only happens on CONFIG_PREEMPT+ due to the conditional call into the scheduler.

I think I see; but I can't reproduce. I use:

  defconfig + CONFIG_PREEMPT + CONFIG_DEBUG_ENTRY

let me try and figure out wtf to do about this :/