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    Subject[PATCH 4.19 286/361] rtc: cmos: Fix non-ACPI undefined reference to `hpet_rtc_interrupt
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Maciej W. Rozycki <macro@linux-mips.org>

    commit d197a253855d2d8e507a003880aab35c4e2473db upstream.

    Fix a commit 311ee9c151ad ("rtc: cmos: allow using ACPI for RTC alarm
    instead of HPET") `rtc-cmos' regression causing a link error:

    drivers/rtc/rtc-cmos.o: In function `cmos_platform_probe':
    rtc-cmos.c:(.init.text+0x33c): undefined reference to `hpet_rtc_interrupt'
    rtc-cmos.c:(.init.text+0x3f4): undefined reference to `hpet_rtc_interrupt'

    with non-ACPI platforms using this driver. The cause is the change of
    the condition guarding the use of `hpet_rtc_interrupt'.

    Previously it was a call to `is_hpet_enabled'. That function is static
    inline and has a hardcoded 0 result for non-ACPI platforms, which imply
    !HPET_EMULATE_RTC. Consequently the compiler optimized the whole block
    away including the reference to `hpet_rtc_interrupt', which never made
    it to the link stage.

    Now the guarding condition is a call to `use_hpet_alarm', which is not
    static inline and therefore the compiler may not be able to prove that
    it actually always returns 0 for non-ACPI platforms. Consequently the
    build breaks with an unsatisfied reference, because `hpet_rtc_interrupt'
    is nowhere defined at link time.

    Fix the problem by marking `use_hpet_alarm' inline. As the `inline'
    keyword serves as an optimization hint rather than a requirement the
    compiler is still free to choose whether inlining will be beneficial or
    not for ACPI platforms.

    Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
    Fixes: 311ee9c151ad ("rtc: cmos: allow using ACPI for RTC alarm instead of HPET")
    Cc: stable@vger.kernel.org # 4.18+
    Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/rtc/rtc-cmos.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/rtc/rtc-cmos.c
    +++ b/drivers/rtc/rtc-cmos.c
    @@ -167,7 +167,7 @@ static inline int hpet_unregister_irq_ha
    #endif

    /* Don't use HPET for RTC Alarm event if ACPI Fixed event is used */
    -static int use_hpet_alarm(void)
    +static inline int use_hpet_alarm(void)
    {
    return is_hpet_enabled() && !use_acpi_alarm;
    }

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