linux-kernel - Re: [PATCH RFC 11/12] time: Convert xen_read

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Message-ID: <CADcy93Ukogi3pzDc2-Gsr2G=iksCB5w9Zap-_GY1pSkfCOVbLQ@mail.gmail.com>
Date:	Wed, 29 Oct 2014 21:04:39 +0800
From:	Xunlei Pang <pang.xunlei@...aro.org>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	xen-devel@...ts.xensource.com
Subject: Re: [PATCH RFC 11/12] time: Convert xen_read_wallclock() to use timespec64

On 27 October 2014 23:35, Stefano Stabellini
<stefano.stabellini@...citrix.com> wrote:
> On Mon, 27 Oct 2014, pang.xunlei wrote:
>> The kernel uses 32-bit signed value(time_t) for seconds since 1970-01-01:00:00:00, so it
>> will overflow at 2038-01-19 03:14:08 on 32-bit systems. We call this "2038 safety" issue.
>>
>> As part of addressing 2038 safety for in-kernel uses, this patch creates no functional change
>> in existing users, converts xen_read_wallclock() to use timespec64 instead of timespec.
>>
>> Signed-off-by: pang.xunlei <pang.xunlei@...aro.org>
>
> Please CC xen-devel@...ts.xenproject.org for Xen related patches.
Ok, apologies for missing this.
>
>
>>  arch/x86/xen/time.c |   31 +++++++++++++++++++------------
>>  1 file changed, 19 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
>> index cf1b591..2ce064a 100644
>> --- a/arch/x86/xen/time.c
>> +++ b/arch/x86/xen/time.c
>> @@ -169,20 +169,33 @@ static cycle_t xen_clocksource_get_cycles(struct clocksource *cs)
>>       return xen_clocksource_read();
>>  }
>>
>> -static void xen_read_wallclock(struct timespec *ts)
>> +static void xen_read_wallclock(struct timespec64 *ts)
>>  {
>> +     struct timespec ts32;
>>       struct shared_info *s = HYPERVISOR_shared_info;
>>       struct pvclock_wall_clock *wall_clock = &(s->wc);
>>          struct pvclock_vcpu_time_info *vcpu_time;
>>
>>       vcpu_time = &get_cpu_var(xen_vcpu)->time;
>> -     pvclock_read_wallclock(wall_clock, vcpu_time, ts);
>> +     /*
>> +      * TODO: [2038 safety] pvclock_read_wallclock() should be changed
>> +      * to use timespec64 for 2038 safety as soon as possible.
>> +      */
>> +     pvclock_read_wallclock(wall_clock, vcpu_time, &ts32);
>> +     *ts = timespec_to_timespec64(ts32);
>>       put_cpu_var(xen_vcpu);
>>  }
>>
>> +/*
>> + * TODO: [2038 safety] xen_get_wallclock() should be changed to use
>> + * timespec64 for 2038 safety as soon as possible.
>> + */
>>  static void xen_get_wallclock(struct timespec *now)
>
> At this point shouldn't you convert xen_get_wallclock to timespec64 too?
This conversion is in the following patches. I'll send the version 2 tomorrow
which will demonstrate this in the first subset.
>
>
>>  {
>> -     xen_read_wallclock(now);
>> +     struct timespec64 now64;
>> +
>> +     xen_read_wallclock(&now64);
>> +     *now = timespec64_to_timespec(now64);
>>  }
>>
>>  static int xen_set_wallclock(const struct timespec *now)
>> @@ -485,8 +498,7 @@ static const struct pv_time_ops xen_time_ops __initconst = {
>>  static void __init xen_time_init(void)
>>  {
>>       int cpu = smp_processor_id();
>> -     struct timespec tp;
>> -     struct timespec64 tp64;
>> +     struct timespec64 tp;
>>
>>       clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC);
>>
>> @@ -497,14 +509,9 @@ static void __init xen_time_init(void)
>>               xen_clockevent = &xen_vcpuop_clockevent;
>>       }
>>
>> -     /*
>> -      * Set initial system time with full resolution.
>> -      * TODO: [2038 safety] xen_read_wallclock() should be changed to use
>> -      * timespec64 for 2038 safety as soon as possible.
>> -      */
>> +     /* Set initial system time with full resolution. */
>>       xen_read_wallclock(&tp);
>> -     tp64 = timespec_to_timespec64(tp);
>> -     do_settimeofday(&tp64);
>> +     do_settimeofday(&tp);
>>
>>       setup_force_cpu_cap(X86_FEATURE_TSC);
>>
>> --
>> 1.7.9.5
>>
>> --
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