From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Will Deacon <will.deacon@arm.com>,
Russell King <linux@armlinux.org.uk>,
Ralf Baechle <ralf@linux-mips.org>,
Mark Salyzyn <salyzyn@android.com>,
Paul Burton <paul.burton@mips.com>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Peter Collingbourne <pcc@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 02/23] kernel: Define gettimeofday vdso common code
Date: Mon, 25 Feb 2019 14:09:55 +0000 [thread overview]
Message-ID: <025bc260-85aa-a04e-b29b-b664f50abc3c@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1902231123030.1666@nanos.tec.linutronix.de>
Hi Thomas,
thank you for your review.
On 23/02/2019 10:34, Thomas Gleixner wrote:
> On Fri, 22 Feb 2019, Vincenzo Frascino wrote:
>> +static notrace int __cvdso_clock_getres(clockid_t clock,
>> + struct __vdso_timespec *res)
>> +{
>> + u64 sec, ns;
>> + u32 msk;
>> +
>> + /* Check for negative values or invalid clocks */
>> + if (unlikely((u32) clock >= MAX_CLOCKS))
>> + goto fallback;
>> +
>> + /*
>> + * Convert the clockid to a bitmask and use it to check which
>> + * clocks are handled in the VDSO directly.
>> + */
>> + msk = 1U << clock;
>> + if (msk & VDSO_HRES) {
>> + /*
>> + * Preserves the behaviour of posix_get_hrtimer_res().
>> + */
>
> So much for the theory.
>
>> + sec = 0;
>> + ns = MONOTONIC_RES_NSEC;
>
> posix_get_hrtimer_res() does:
>
> sec = 0;
> ns = hrtimer_resolution;
>
> and hrtimer_resolution depends on the enablement of high resolution timers
> either compile or run time.
>
> So you need to have a copy of hrtimer_resolution in the vdso data and use
> that.
>
I agree, MONOTONIC_RES_NSEC can be HIGH_RES_NSEC or LOW_RES_NSEC depending on
the HIGH_RES_TIMERS configuration option, but does not cover the run time
switch. I will add a copy of hrtimer_resolution in the vdso data in the next
iteration of the patches.
I had a look at the other implementations as well, and it seems that all the
architectures that currently implement getres() make the same wrong assumption I
made. I am going to provide a separate patch set that targets this.
>> + } else if (msk & VDSO_COARSE) {
>> + /*
>> + * Preserves the behaviour of posix_get_coarse_res().
>> + */
>> + ns = LOW_RES_NSEC;
>> + sec = __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
>
> Do we allow CONFIG_HZ = 1?
>
I had a closer look at it today and seems that jiffies.h supports CONFIG_HZ=12
as a minimum case. Hence I think it should be safe to remove __iter_div_u64_rem
and set sec=0 in this case.
> Thanks,
>
> tglx
>
--
Regards,
Vincenzo
WARNING: multiple messages have this Message-ID (diff)
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>, Arnd Bergmann <arnd@arndb.de>,
Russell King <linux@armlinux.org.uk>,
Ralf Baechle <ralf@linux-mips.org>,
Paul Burton <paul.burton@mips.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Mark Salyzyn <salyzyn@android.com>,
Peter Collingbourne <pcc@google.com>,
Shuah Khan <shuah@kernel.org>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>
Subject: Re: [PATCH v5 02/23] kernel: Define gettimeofday vdso common code
Date: Mon, 25 Feb 2019 14:09:55 +0000 [thread overview]
Message-ID: <025bc260-85aa-a04e-b29b-b664f50abc3c@arm.com> (raw)
Message-ID: <20190225140955.NzQliMXZoKhdJ1cOYDfu2zHpyiROdxUsuNRLhoQS6fY@z> (raw)
In-Reply-To: <alpine.DEB.2.21.1902231123030.1666@nanos.tec.linutronix.de>
Hi Thomas,
thank you for your review.
On 23/02/2019 10:34, Thomas Gleixner wrote:
> On Fri, 22 Feb 2019, Vincenzo Frascino wrote:
>> +static notrace int __cvdso_clock_getres(clockid_t clock,
>> + struct __vdso_timespec *res)
>> +{
>> + u64 sec, ns;
>> + u32 msk;
>> +
>> + /* Check for negative values or invalid clocks */
>> + if (unlikely((u32) clock >= MAX_CLOCKS))
>> + goto fallback;
>> +
>> + /*
>> + * Convert the clockid to a bitmask and use it to check which
>> + * clocks are handled in the VDSO directly.
>> + */
>> + msk = 1U << clock;
>> + if (msk & VDSO_HRES) {
>> + /*
>> + * Preserves the behaviour of posix_get_hrtimer_res().
>> + */
>
> So much for the theory.
>
>> + sec = 0;
>> + ns = MONOTONIC_RES_NSEC;
>
> posix_get_hrtimer_res() does:
>
> sec = 0;
> ns = hrtimer_resolution;
>
> and hrtimer_resolution depends on the enablement of high resolution timers
> either compile or run time.
>
> So you need to have a copy of hrtimer_resolution in the vdso data and use
> that.
>
I agree, MONOTONIC_RES_NSEC can be HIGH_RES_NSEC or LOW_RES_NSEC depending on
the HIGH_RES_TIMERS configuration option, but does not cover the run time
switch. I will add a copy of hrtimer_resolution in the vdso data in the next
iteration of the patches.
I had a look at the other implementations as well, and it seems that all the
architectures that currently implement getres() make the same wrong assumption I
made. I am going to provide a separate patch set that targets this.
>> + } else if (msk & VDSO_COARSE) {
>> + /*
>> + * Preserves the behaviour of posix_get_coarse_res().
>> + */
>> + ns = LOW_RES_NSEC;
>> + sec = __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
>
> Do we allow CONFIG_HZ = 1?
>
I had a closer look at it today and seems that jiffies.h supports CONFIG_HZ=12
as a minimum case. Hence I think it should be safe to remove __iter_div_u64_rem
and set sec=0 in this case.
> Thanks,
>
> tglx
>
--
Regards,
Vincenzo
WARNING: multiple messages have this Message-ID (diff)
From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Will Deacon <will.deacon@arm.com>,
Russell King <linux@armlinux.org.uk>,
Ralf Baechle <ralf@linux-mips.org>,
Mark Salyzyn <salyzyn@android.com>,
Paul Burton <paul.burton@mips.com>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Peter Collingbourne <pcc@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 02/23] kernel: Define gettimeofday vdso common code
Date: Mon, 25 Feb 2019 14:09:55 +0000 [thread overview]
Message-ID: <025bc260-85aa-a04e-b29b-b664f50abc3c@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1902231123030.1666@nanos.tec.linutronix.de>
Hi Thomas,
thank you for your review.
On 23/02/2019 10:34, Thomas Gleixner wrote:
> On Fri, 22 Feb 2019, Vincenzo Frascino wrote:
>> +static notrace int __cvdso_clock_getres(clockid_t clock,
>> + struct __vdso_timespec *res)
>> +{
>> + u64 sec, ns;
>> + u32 msk;
>> +
>> + /* Check for negative values or invalid clocks */
>> + if (unlikely((u32) clock >= MAX_CLOCKS))
>> + goto fallback;
>> +
>> + /*
>> + * Convert the clockid to a bitmask and use it to check which
>> + * clocks are handled in the VDSO directly.
>> + */
>> + msk = 1U << clock;
>> + if (msk & VDSO_HRES) {
>> + /*
>> + * Preserves the behaviour of posix_get_hrtimer_res().
>> + */
>
> So much for the theory.
>
>> + sec = 0;
>> + ns = MONOTONIC_RES_NSEC;
>
> posix_get_hrtimer_res() does:
>
> sec = 0;
> ns = hrtimer_resolution;
>
> and hrtimer_resolution depends on the enablement of high resolution timers
> either compile or run time.
>
> So you need to have a copy of hrtimer_resolution in the vdso data and use
> that.
>
I agree, MONOTONIC_RES_NSEC can be HIGH_RES_NSEC or LOW_RES_NSEC depending on
the HIGH_RES_TIMERS configuration option, but does not cover the run time
switch. I will add a copy of hrtimer_resolution in the vdso data in the next
iteration of the patches.
I had a look at the other implementations as well, and it seems that all the
architectures that currently implement getres() make the same wrong assumption I
made. I am going to provide a separate patch set that targets this.
>> + } else if (msk & VDSO_COARSE) {
>> + /*
>> + * Preserves the behaviour of posix_get_coarse_res().
>> + */
>> + ns = LOW_RES_NSEC;
>> + sec = __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
>
> Do we allow CONFIG_HZ = 1?
>
I had a closer look at it today and seems that jiffies.h supports CONFIG_HZ=12
as a minimum case. Hence I think it should be safe to remove __iter_div_u64_rem
and set sec=0 in this case.
> Thanks,
>
> tglx
>
--
Regards,
Vincenzo
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next prev parent reply other threads:[~2019-02-25 14:09 UTC|newest]
Thread overview: 178+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-22 12:24 [PATCH v5 00/23] Unify vDSOs across more architectures Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 01/23] kernel: Standardize vdso_datapage Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:58 ` Mark Rutland
2019-02-22 12:58 ` Mark Rutland
2019-02-22 12:58 ` Mark Rutland
2019-02-23 16:51 ` Thomas Gleixner
2019-02-23 16:51 ` Thomas Gleixner
2019-02-23 16:51 ` Thomas Gleixner
2019-02-27 14:23 ` Vincenzo Frascino
2019-02-27 14:23 ` Vincenzo Frascino
2019-02-27 14:23 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 02/23] kernel: Define gettimeofday vdso common code Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 13:34 ` Mark Rutland
2019-02-22 13:34 ` Mark Rutland
2019-02-22 13:34 ` Mark Rutland
2019-02-22 13:49 ` Arnd Bergmann
2019-02-22 13:49 ` Arnd Bergmann
2019-02-22 13:49 ` Arnd Bergmann
2019-02-22 14:36 ` Arnd Bergmann
2019-02-22 14:36 ` Arnd Bergmann
2019-02-22 14:36 ` Arnd Bergmann
2019-02-27 14:52 ` Vincenzo Frascino
2019-02-27 14:52 ` Vincenzo Frascino
2019-02-27 14:52 ` Vincenzo Frascino
2019-02-28 9:29 ` Arnd Bergmann
2019-02-28 9:29 ` Arnd Bergmann
2019-02-28 9:29 ` Arnd Bergmann
2019-02-28 11:58 ` [PATCH 1/2] vdso: use fixed-size time types Arnd Bergmann
2019-02-28 11:58 ` Arnd Bergmann
2019-02-28 11:58 ` Arnd Bergmann
2019-02-28 11:58 ` [PATCH 2/2] vdso: add clock_gettime64 Arnd Bergmann
2019-02-28 11:58 ` Arnd Bergmann
2019-02-28 11:58 ` Arnd Bergmann
2019-02-28 13:42 ` [PATCH 1/2] vdso: use fixed-size time types Thomas Gleixner
2019-02-28 13:42 ` Thomas Gleixner
2019-02-28 13:42 ` Thomas Gleixner
2019-02-28 13:45 ` Vincenzo Frascino
2019-02-28 13:45 ` Vincenzo Frascino
2019-02-28 13:45 ` Vincenzo Frascino
2019-02-23 10:34 ` [PATCH v5 02/23] kernel: Define gettimeofday vdso common code Thomas Gleixner
2019-02-23 10:34 ` Thomas Gleixner
2019-02-23 10:34 ` Thomas Gleixner
2019-02-25 14:09 ` Vincenzo Frascino [this message]
2019-02-25 14:09 ` Vincenzo Frascino
2019-02-25 14:09 ` Vincenzo Frascino
2019-02-23 17:31 ` Thomas Gleixner
2019-02-23 17:31 ` Thomas Gleixner
2019-02-23 17:31 ` Thomas Gleixner
2019-02-27 13:47 ` Vincenzo Frascino
2019-02-27 13:47 ` Vincenzo Frascino
2019-02-27 13:47 ` Vincenzo Frascino
2019-02-27 15:49 ` Thomas Gleixner
2019-02-27 15:49 ` Thomas Gleixner
2019-02-27 15:49 ` Thomas Gleixner
2019-02-27 16:06 ` Vincenzo Frascino
2019-02-27 16:06 ` Vincenzo Frascino
2019-02-27 16:06 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 03/23] arm64: Build vDSO with -ffixed-x18 Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 04/23] arm64: Substitute gettimeofday with C implementation Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 13:42 ` Mark Rutland
2019-02-22 13:42 ` Mark Rutland
2019-02-22 13:42 ` Mark Rutland
2019-02-22 12:24 ` [PATCH v5 05/23] arm64: compat: Alloc separate pages for vectors and sigpage Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 06/23] arm64: compat: Split kuser32 Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 07/23] arm64: compat: Refactor aarch32_alloc_vdso_pages() Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 08/23] arm64: compat: Add KUSER_HELPERS config option Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 14:04 ` Mark Rutland
2019-02-22 14:04 ` Mark Rutland
2019-02-22 14:04 ` Mark Rutland
2019-02-22 14:09 ` Russell King - ARM Linux admin
2019-02-22 14:09 ` Russell King - ARM Linux admin
2019-02-22 14:09 ` Russell King - ARM Linux admin
2019-02-26 12:10 ` Vincenzo Frascino
2019-02-26 12:10 ` Vincenzo Frascino
2019-02-26 12:10 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 09/23] arm64: compat: Add missing syscall numbers Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 10/23] arm64: compat: Expose signal related structures Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 11/23] arm64: compat: Generate asm offsets for signals Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 14:22 ` Mark Rutland
2019-02-22 14:22 ` Mark Rutland
2019-02-22 14:22 ` Mark Rutland
2019-02-22 12:24 ` [PATCH v5 12/23] lib: vdso: Add compat support Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 13/23] arm64: compat: Add vDSO Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 14:32 ` Mark Rutland
2019-02-22 14:32 ` Mark Rutland
2019-02-22 14:32 ` Mark Rutland
2019-02-22 12:24 ` [PATCH v5 14/23] arm64: Refactor vDSO code Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 14:37 ` Mark Rutland
2019-02-22 14:37 ` Mark Rutland
2019-02-22 14:37 ` Mark Rutland
2019-02-22 12:24 ` [PATCH v5 15/23] arm64: compat: vDSO setup for compat layer Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 16/23] arm64: elf: vDSO code page discovery Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 17/23] arm64: compat: Get sigreturn trampolines from vDSO Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 18/23] arm64: Add vDSO compat support Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 19/23] arm64: Enable compat vDSO support Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 14:39 ` Mark Rutland
2019-02-22 14:39 ` Mark Rutland
2019-02-22 14:39 ` Mark Rutland
2019-02-22 14:41 ` Mark Rutland
2019-02-22 14:41 ` Mark Rutland
2019-02-22 14:41 ` Mark Rutland
2019-02-22 12:24 ` [PATCH v5 20/23] arm: Add support for generic vDSO Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 21/23] mips: " Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 22/23] x86: " Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-23 10:45 ` Thomas Gleixner
2019-02-23 10:45 ` Thomas Gleixner
2019-02-23 10:45 ` Thomas Gleixner
2019-02-27 16:18 ` Vincenzo Frascino
2019-02-27 16:18 ` Vincenzo Frascino
2019-02-27 16:18 ` Vincenzo Frascino
2019-02-22 12:24 ` [PATCH v5 23/23] kselftest: Extend vDSO selftest Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-22 12:24 ` Vincenzo Frascino
2019-02-23 17:39 ` [PATCH v5 00/23] Unify vDSOs across more architectures Thomas Gleixner
2019-02-23 17:39 ` Thomas Gleixner
2019-02-23 17:39 ` Thomas Gleixner
2019-02-28 11:40 ` Arnd Bergmann
2019-02-28 11:40 ` Arnd Bergmann
2019-02-28 12:09 ` Vincenzo Frascino
2019-02-28 12:09 ` Vincenzo Frascino
2019-02-28 12:38 ` Arnd Bergmann
2019-02-28 12:38 ` Arnd Bergmann
2019-02-28 12:38 ` Arnd Bergmann
2019-02-28 12:42 ` Vincenzo Frascino
2019-02-28 12:42 ` Vincenzo Frascino
2019-02-28 12:42 ` Vincenzo Frascino
2019-02-28 13:54 ` Arnd Bergmann
2019-02-28 13:54 ` Arnd Bergmann
2019-02-28 13:54 ` Arnd Bergmann
2019-02-28 15:51 ` Vincenzo Frascino
2019-02-28 15:51 ` Vincenzo Frascino
2019-02-28 15:51 ` Vincenzo Frascino
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