linux-kernel - Re: [PATCHv3 06/27] posix-timers/timens: Take into account clock offsets

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Date:   Thu, 25 Apr 2019 23:45:06 +0200 (CEST)
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>,
        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>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv3 06/27] posix-timers/timens: Take into account clock
 offsets

On Thu, 25 Apr 2019, Dmitry Safonov wrote:

> From: Andrei Vagin <avagin@...il.com>
> 
> Wire timer_settime() syscall into time namespace virtualization.
> 
> Signed-off-by: Andrei Vagin <avagin@...nvz.org>
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
>  kernel/time/alarmtimer.c   | 3 +++
>  kernel/time/posix-timers.c | 2 ++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
> index 31f99361342e..23f5c39c8d23 100644
> --- a/kernel/time/alarmtimer.c
> +++ b/kernel/time/alarmtimer.c
> @@ -26,6 +26,7 @@
>  #include <linux/freezer.h>
>  #include <linux/compat.h>
>  #include <linux/module.h>
> +#include <linux/time_namespace.h>
>  
>  #include "posix-timers.h"
>  
> @@ -621,6 +622,8 @@ static void alarm_timer_arm(struct k_itimer *timr, ktime_t expires,
>  
>  	if (!absolute)
>  		expires = ktime_add_safe(expires, base->gettime());
> +	else
> +		expires = timens_ktime_to_host(base->base_clockid, expires);
>
>  	if (sigev_none)
>  		alarm->node.expires = expires;
>  	else
> diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
> index a723e63d55fd..7922731f98cd 100644
> --- a/kernel/time/posix-timers.c
> +++ b/kernel/time/posix-timers.c
> @@ -803,6 +803,8 @@ static void common_hrtimer_arm(struct k_itimer *timr, ktime_t expires,
>  
>  	if (!absolute)
>  		expires = ktime_add_safe(expires, timer->base->get_time());
> +	else
> +		expires = timens_ktime_to_host(timer->base->clockid, expires);
>  	hrtimer_set_expires(timer, expires);

So you have now two places where you do that adjustment. Why? And why in
the timer_arm() callback? The obvious place to do that is in
common_timer_set().

-	expires = timespec64_to_ktime(new_setting->it_value);
+	expires = timespec64_to_host(timr->it_clock, &new_setting->it_value);

static ktime_t timespec64_to_host(clockid_t which, struct timespec64 val)
{
	ktime_t expires = timespec64_to_ktime(val);

#ifdef NAMESPACE
	switch (which) {
	case CLOCK_MONOTONIC:
		return timens_sub_monotonic(expires);
	case CLOCK_BOOTTINE:
	case CLOCK_BOOTTIME_ALARM:
		return timens_sub_boottime(expires);
	}
#endif
	return expires;
}

Thanks,

	tglx