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From: Thomas Gleixner <tglx@kernel.org>
To: "Thomas Weißschuh" <linux@weissschuh.net>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Vincenzo Frascino" <vincenzo.frascino@arm.com>,
	"Shuah Khan" <shuah@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	"Thomas Weißschuh" <linux@weissschuh.net>
Subject: Re: [PATCH v2 2/3] vdso/gettimeofday: Add support for CLOCK_BOOTTIME_ALARM
Date: Thu, 15 Oct 2026 15:43:59 +0200	[thread overview]
Message-ID: <87ld7zdqow.ffs@fw13> (raw)
In-Reply-To: <20260929-vdso-alarm-clocks-v2-2-a7af4089a698@weissschuh.net>

On Tue, Sep 29 2026 at 22:24, Thomas Weißschuh wrote:

> CLOCK_BOOTTIME_ALARM behaves exactly as CLOCK_BOOTTIME as far as the
> vDSO is concerned. The vDSO library can handle it automatically
> correctly. Only the basetime needs to be maintained during the tick.
>
> The namespace offset is already set correctly, although it was not
> used before.
>
> Reuse the CLOCK_BOOTTIME basetime for CLOCK_BOOTTIME_ALARM and update
> the userspace hres clock mask to include CLOCK_BOOTTIME_ALARM.

It behaves the same way, but ALARM clock IDs require a RTC device. See
alarm_clock_get_timespec().

So the VDSO and the syscall will disagree when there is no RTC
available...

Thanks,

        tglx

  reply	other threads:[~2026-10-15 13:44 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-29 20:24 [PATCH v2 0/3] vdso/gettimeofday: Add support for ALARM clocks Thomas Weißschuh
2026-09-29 20:24 ` [PATCH v2 1/3] selftests: vDSO: vdso_test_abi: Also test " Thomas Weißschuh
2026-09-29 20:24 ` [PATCH v2 2/3] vdso/gettimeofday: Add support for CLOCK_BOOTTIME_ALARM Thomas Weißschuh
2026-10-15 13:43   ` Thomas Gleixner [this message]
2026-09-29 20:24 ` [PATCH v2 3/3] vdso/gettimeofday: Add support for CLOCK_REALTIME_ALARM Thomas Weißschuh

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