From: Thomas Gleixner <tglx@linutronix.de> To: Will Deacon <will.deacon@arm.com> Cc: linux-arch@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>, marc.zyngier@arm.com, Catalin Marinas <catalin.marinas@arm.com>, Daniel Lezcano <daniel.lezcano@linaro.org>, Russell King <linux@armlinux.org.uk>, Ralf Baechle <ralf@linux-mips.org>, Mark Salyzyn <salyzyn@android.com>, Paul Burton <paul.burton@mips.com>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Peter Collingbourne <pcc@google.com>, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 06/28] kernel: Define gettimeofday vdso common code Date: Wed, 13 Feb 2019 20:35:32 +0100 (CET) [thread overview] Message-ID: <alpine.DEB.2.21.1902132033270.1659@nanos.tec.linutronix.de> (raw) In-Reply-To: <20190213170413.GE6346@brain-police> On Wed, 13 Feb 2019, Will Deacon wrote: > On Fri, Feb 08, 2019 at 08:30:25PM +0100, Thomas Gleixner wrote: > > > > How is the in kernel ktime_get() correctness guaranteed then? > > Luck. > > I think we'll have to introduce a dummy dependent stack read into our > counter accessor so that it's ordered by the smp_rmb(). Example diff > below, which I'll roll into a proper patch series later on. Yikes. > static inline u64 arch_counter_get_cntpct(void) > { > + u64 cnt, tmp; > + > isb(); > - return arch_timer_reg_read_stable(cntpct_el0); > + cnt = arch_timer_reg_read_stable(cntpct_el0); > + > + /* > + * This insanity brought to you by speculative, out-of-order system > + * register reads, sequence locks and Thomas Gleixner. ROTFL
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de> To: Will Deacon <will.deacon@arm.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Catalin Marinas <catalin.marinas@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>, marc.zyngier@arm.com Subject: Re: [PATCH v2 06/28] kernel: Define gettimeofday vdso common code Date: Wed, 13 Feb 2019 20:35:32 +0100 (CET) [thread overview] Message-ID: <alpine.DEB.2.21.1902132033270.1659@nanos.tec.linutronix.de> (raw) Message-ID: <20190213193532.CCwnf3PjsskASupIWzJdxqf9NTpoEnl_NFX5uuddTkE@z> (raw) In-Reply-To: <20190213170413.GE6346@brain-police> On Wed, 13 Feb 2019, Will Deacon wrote: > On Fri, Feb 08, 2019 at 08:30:25PM +0100, Thomas Gleixner wrote: > > > > How is the in kernel ktime_get() correctness guaranteed then? > > Luck. > > I think we'll have to introduce a dummy dependent stack read into our > counter accessor so that it's ordered by the smp_rmb(). Example diff > below, which I'll roll into a proper patch series later on. Yikes. > static inline u64 arch_counter_get_cntpct(void) > { > + u64 cnt, tmp; > + > isb(); > - return arch_timer_reg_read_stable(cntpct_el0); > + cnt = arch_timer_reg_read_stable(cntpct_el0); > + > + /* > + * This insanity brought to you by speculative, out-of-order system > + * register reads, sequence locks and Thomas Gleixner. ROTFL
next prev parent reply other threads:[~2019-02-13 19:35 UTC|newest] Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-29 17:05 [PATCH v2 00/28] Unify vDSOs across more architectures Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 01/28] kernel: Standardize vdso_datapage Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 22:39 ` Thomas Gleixner 2018-11-29 22:39 ` Thomas Gleixner 2018-12-11 13:22 ` Vincenzo Frascino 2018-12-11 13:22 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 02/28] kernel: Add Monotonic boot time support Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 03/28] kernel: Add International Atomic Time support Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 04/28] kernel: Add masks support for Raw and NTP time Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 22:41 ` Thomas Gleixner 2018-11-29 22:41 ` Thomas Gleixner 2018-12-11 13:24 ` Vincenzo Frascino 2018-12-11 13:24 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 05/28] kernel: Add clock_mode support Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 06/28] kernel: Define gettimeofday vdso common code Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 20:42 ` Arnd Bergmann 2018-11-29 20:42 ` Arnd Bergmann 2018-12-11 13:39 ` Vincenzo Frascino 2018-12-11 13:39 ` Vincenzo Frascino 2018-12-11 21:41 ` Arnd Bergmann 2018-12-11 21:41 ` Arnd Bergmann 2018-12-13 9:46 ` Vincenzo Frascino 2018-12-13 9:46 ` Vincenzo Frascino 2018-11-29 22:11 ` Thomas Gleixner 2018-11-29 22:11 ` Thomas Gleixner 2018-11-30 14:29 ` Arnd Bergmann 2018-11-30 14:29 ` Arnd Bergmann 2018-12-11 14:02 ` Vincenzo Frascino 2018-12-11 14:02 ` Vincenzo Frascino 2018-12-07 17:53 ` Will Deacon 2018-12-07 17:53 ` Will Deacon 2019-02-08 17:35 ` Will Deacon 2019-02-08 17:35 ` Will Deacon 2019-02-08 19:28 ` Thomas Gleixner 2019-02-08 19:28 ` Thomas Gleixner 2019-02-08 19:30 ` Thomas Gleixner 2019-02-08 19:30 ` Thomas Gleixner 2019-02-13 17:04 ` Will Deacon 2019-02-13 17:04 ` Will Deacon 2019-02-13 19:35 ` Thomas Gleixner [this message] 2019-02-13 19:35 ` Thomas Gleixner 2019-02-13 17:05 ` Will Deacon 2019-02-13 17:05 ` Will Deacon 2018-12-11 13:54 ` Vincenzo Frascino 2018-12-11 13:54 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 07/28] arm64: Build vDSO with -ffixed-x18 Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 08/28] arm64: Substitute gettimeofday with C implementation Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 09/28] arm64: compat: Alloc separate pages for vectors and sigpage Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 10/28] arm64: compat: Split kuser32 Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 11/28] arm64: compat: Refactor aarch32_alloc_vdso_pages() Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 12/28] arm64: compat: Add KUSER_HELPERS config option Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 13/28] arm64: compat: Add missing syscall numbers Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 14/28] arm64: compat: Expose signal related structures Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 15/28] arm64: compat: Generate asm offsets for signals Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 16/28] lib: vdso: Add compat support Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 17/28] arm64: compat: Add vDSO Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 18/28] arm64: Refactor vDSO code Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 19/28] arm64: compat: vDSO setup for compat layer Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 20/28] arm64: elf: vDSO code page discovery Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 21/28] arm64: compat: Get sigreturn trampolines from vDSO Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 22/28] arm64: Add vDSO compat support Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 23/28] arm64: Enable compat vDSO support Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 24/28] arm: Add support for generic vDSO Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-12-10 22:13 ` Mark Salyzyn 2018-12-10 22:13 ` Mark Salyzyn 2018-12-11 14:15 ` Vincenzo Frascino 2018-12-11 14:15 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 25/28] mips: Introduce vdso_direct Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 26/28] clock: csrc-4k: Add support for vdso_direct Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 27/28] clock: gic-timer: " Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino 2018-11-29 17:05 ` [PATCH v2 28/28] mips: Add support for generic vDSO Vincenzo Frascino 2018-11-29 17:05 ` Vincenzo Frascino
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