linux-kernel - Re: [PATCH 07/32] timens/kernel: Take into account timens clock offsets in clock

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Date:   Fri, 8 Feb 2019 08:56:25 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dmitry Safonov <dima@...sta.com>
cc:     linux-kernel@...r.kernel.org, Andrei Vagin <avagin@...il.com>,
        Adrian Reber <adrian@...as.de>,
        Andrei Vagin <avagin@...nvz.org>,
        Andy Lutomirski <luto@...nel.org>,
        Andy Tucker <agtucker@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jeff Dike <jdike@...toit.com>, Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 07/32] timens/kernel: Take into account timens clock
 offsets in clock_nanosleep

On Wed, 6 Feb 2019, Dmitry Safonov wrote:
>  
> @@ -1721,9 +1722,16 @@ long hrtimer_nanosleep(const struct timespec64 *rqtp,
>  {
>  	struct restart_block *restart;
>  	struct hrtimer_sleeper t;
> +	struct timespec64 tp;
>  	int ret = 0;
>  	u64 slack;
>  
> +	if (!(mode & HRTIMER_MODE_REL)) {
> +		tp = *rqtp;
> +		rqtp = &tp;

So every invocation of hrtimer_nanosleep() gains a copy of the timespec64
even if the namespace muck is disabled.

The only relevant caller of this is common_nsleep(). So it might make sense
to have common_nsleep() separated for CLOCK_MONOTONIC/BOOTTIME and handle
the thing there. That again avoids the switch() to and out of line calls.

Thanks,

	tglx