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Date:   Fri, 8 Feb 2019 08:56:25 +0100 (CET)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Dmitry Safonov <dima@arista.com>
cc:     linux-kernel@vger.kernel.org, Andrei Vagin <avagin@gmail.com>,
        Adrian Reber <adrian@lisas.de>,
        Andrei Vagin <avagin@openvz.org>,
        Andy Lutomirski <luto@kernel.org>,
        Andy Tucker <agtucker@google.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Jeff Dike <jdike@addtoit.com>, Oleg Nesterov <oleg@redhat.com>,
        Pavel Emelyanov <xemul@virtuozzo.com>,
        Shuah Khan <shuah@kernel.org>,
        containers@lists.linux-foundation.org, criu@openvz.org,
        linux-api@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH 07/32] timens/kernel: Take into account timens clock
 offsets in clock_nanosleep
In-Reply-To: <20190206001107.16488-8-dima@arista.com>
Message-ID: <alpine.DEB.2.21.1902072242220.1645@nanos.tec.linutronix.de>
References: <20190206001107.16488-1-dima@arista.com> <20190206001107.16488-8-dima@arista.com>
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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