From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: y2038 Mailman List <y2038@lists.linaro.org>,
Tyler Baicar <tbaicar@codeaurora.org>,
Will Deacon <will.deacon@arm.com>, Ingo Molnar <mingo@kernel.org>,
Borislav Petkov <bp@suse.de>,
Yazen Ghannam <yazen.ghannam@amd.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
gengdongjiu <gengdongjiu@huawei.com>,
linux-efi <linux-efi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] efi: cper: avoid using get_seconds()
Date: Mon, 18 Jun 2018 17:56:48 +0200 [thread overview]
Message-ID: <CAKv+Gu9zYJk+ubcn8ngqsXPBbxWM-S5kUWAHfe_zKDm1=FWB4w@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a0xkPrDhoHaUzcN++b7TEh3v_a=VkP6VX9_FD56pG1A6w@mail.gmail.com>
On 18 June 2018 at 17:54, Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Jun 18, 2018 at 5:50 PM, Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
>> On 18 June 2018 at 17:49, Arnd Bergmann <arnd@arndb.de> wrote:
>>> On Mon, Jun 18, 2018 at 5:47 PM, Ard Biesheuvel
>>> <ard.biesheuvel@linaro.org> wrote:
>>>> On 18 June 2018 at 16:17, Arnd Bergmann <arnd@arndb.de> wrote:
>>>
>>>>> - atomic64_set(&seq, ((u64)get_seconds()) << 32);
>>>>> + if (!atomic64_read(&seq)) {
>>>>> + time64_t time = ktime_get_real_seconds();
>>>>> +
>>>>> + /*
>>>>> + * This code is unlikely to still be needed in year 2106,
>>>>> + * but just in case, let's use a few more bits for timestamps
>>>>> + * after y2038 to be sure they keep increasing monotonically
>>>>> + * for the next few hundred years...
>>>>> + */
>>>>> + if (time < 0x80000000)
>>>>> + atomic64_set(&seq, (ktime_get_real_seconds()) << 32);
>>>>> + else
>>>>> + atomic64_set(&seq, 0x8000000000000000ull |
>>>>> + ktime_get_real_seconds() << 24);
>>>>> + }
>>>>
>>>> Given that these values are never decoded and interpreted as
>>>> timestamps, can't we simply switch to the second flavour immediately?
>>>
>>> I considered that, but the downside would be that all future filenames would
>>> come before all past file names.
>>
>> Won't we have that same problem in 2038?
>
> No, it goes from 0x7fffffff00000000 to 0x8000000000000000, followed
> by 0x8000000001000000.
>
Ah, right. I'm with you now :-)
I'll queue this in the efi tree.
prev parent reply other threads:[~2018-06-18 15:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-18 14:17 [PATCH] efi: cper: avoid using get_seconds() Arnd Bergmann
2018-06-18 15:47 ` Ard Biesheuvel
2018-06-18 15:49 ` Arnd Bergmann
2018-06-18 15:50 ` Ard Biesheuvel
2018-06-18 15:54 ` Arnd Bergmann
2018-06-18 15:56 ` Ard Biesheuvel [this message]
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