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Message-ID: <CAJuCfpHvNjFQYU0zHOuang2mNOLNHHiNfaWACPWuP4mSMX_OmQ@mail.gmail.com>
Date: Wed, 3 Jul 2024 21:07:56 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
vincent.guittot@...aro.org, kent.overstreet@...ux.dev,
linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 1/1] sched.h: always_inline alloc_tag_{save|restore} to
fix modpost warnings
On Wed, Jul 3, 2024 at 8:54 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 3 Jul 2024 20:46:11 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > Ok, I confirmed that the warning is happening due to the access to
> > "current" from alloc_tag_save()/alloc_tag_restore() functions. I guess
> > when these functions access "thread_info" variable:
> > https://elixir.bootlin.com/linux/v6.10-rc6/source/arch/xtensa/include/asm/thread_info.h#L96,
> > compiler flags that because the variable is on the stack of an __init
> > function while alloc_tag_save()/alloc_tag_restore() when not inlined
> > are from .text section.
>
> Well, is the warning legitimate? I don't see why an automatic variable
> of an __init function should be considered to be .init storage - we can
> assume it won't become an invalid reference while the .init function is
> executing?
I don't think it's really a problem. __init function is executing, it
calls a function from .text (say alloc_tag_save() that was not
inlined) which in turn calls get_current(), which returns a pointer
somewhere inside __initdata. That should be fine since this can only
happen during init stage. If this call happens after init,
get_current() can't return a pointer from __initdata. If it does then
we have a much bigger problem.
>
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