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 <18431bad-8595-143b-e8af-14e448af871c@intel.com>
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From:   Uros Bizjak <ubizjak@gmail.com>
Date:   Wed, 22 Mar 2023 21:34:16 +0100
Message-ID: <CAFULd4YF7L2puma8O9m_hodjRP9tOyBDixpY-=ShPHjdbX8cGA@mail.gmail.com>
Subject: Re: [PATCH v2] x86/ACPI/boot: Improve __acpi_acquire_global_lock
To:     Dave Hansen <dave.hansen@intel.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>, x86@kernel.org,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Len Brown <lenb@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>
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On Wed, Mar 22, 2023 at 7:34=E2=80=AFPM Dave Hansen <dave.hansen@intel.com>=
 wrote:
>
> On 3/22/23 11:24, Rafael J. Wysocki wrote:
> > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > or please let me know if you want me to pick this up (in which case it
> > will require an ACK from one of the x86 maintainers).
>
> I'll pull it into x86/acpi.  I'm kinda shocked the compiler is so
> clueless, but this makes the C code more readable anyway.  Win/win, I gue=
ss.

Please note that the return form __acpi_{acquire,release}_global_lock
is actually used as bool:

acenv.h:

int __acpi_acquire_global_lock(unsigned int *lock);
int __acpi_release_global_lock(unsigned int *lock);

#define ACPI_ACQUIRE_GLOBAL_LOCK(facs, Acq) \
((Acq) =3D __acpi_acquire_global_lock(&facs->global_lock))

#define ACPI_RELEASE_GLOBAL_LOCK(facs, Acq) \
((Acq) =3D __acpi_release_global_lock(&facs->global_lock))

evglock.c:

acpi_status acpi_ev_acquire_global_lock(u16 timeout)
{
    ...
    u8 acquired =3D FALSE;
    ...
    ACPI_ACQUIRE_GLOBAL_LOCK(acpi_gbl_FACS, acquired);
    if (acquired) ...
}

acpi_status acpi_ev_release_global_lock(void)
{
    u8 pending =3D FALSE;
    ...
   ACPI_RELEASE_GLOBAL_LOCK(acpi_gbl_FACS, pending);
   if (pending) ...
}

These functions are also defined for ia64, so I didn't want to change
the return value. But ia64 is going to be retired, and this opens the
optimization opportunity.

Uros.