From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Brendan Gregg <bgregg@netflix.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
John Stultz <john.stultz@linaro.org>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: [PATCH 4.7 03/31] timekeeping: Fix __ktime_get_fast_ns() regression
Date: Fri, 14 Oct 2016 14:54:47 +0200 [thread overview]
Message-ID: <20161014122715.396623495@linuxfoundation.org> (raw)
In-Reply-To: <20161014122715.235592611@linuxfoundation.org>
4.7-stable review patch. If anyone has any objections, please let me know.
------------------
From: John Stultz <john.stultz@linaro.org>
commit 58bfea9532552d422bde7afa207e1a0f08dffa7d upstream.
In commit 27727df240c7 ("Avoid taking lock in NMI path with
CONFIG_DEBUG_TIMEKEEPING"), I changed the logic to open-code
the timekeeping_get_ns() function, but I forgot to include
the unit conversion from cycles to nanoseconds, breaking the
function's output, which impacts users like perf.
This results in bogus perf timestamps like:
swapper 0 [000] 253.427536: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426573: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426687: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426800: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.426905: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427022: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427127: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427239: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427346: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 254.427463: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 255.426572: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
Instead of more reasonable expected timestamps like:
swapper 0 [000] 39.953768: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.064839: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.175956: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.287103: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.398217: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.509324: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.620437: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.731546: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.842654: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 40.953772: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
swapper 0 [000] 41.064881: 111111111 cpu-clock: ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
Add the proper use of timekeeping_delta_to_ns() to convert
the cycle delta to nanoseconds as needed.
Thanks to Brendan and Alexei for finding this quickly after
the v4.8 release. Unfortunately the problematic commit has
landed in some -stable trees so they'll need this fix as
well.
Many apologies for this mistake. I'll be looking to add a
perf-clock sanity test to the kselftest timers tests soon.
Fixes: 27727df240c7 "timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING"
Reported-by: Brendan Gregg <bgregg@netflix.com>
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Tested-and-reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1475636148-26539-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/time/timekeeping.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -403,8 +403,11 @@ static __always_inline u64 __ktime_get_f
tkr = tkf->base + (seq & 0x01);
now = ktime_to_ns(tkr->base);
- now += clocksource_delta(tkr->read(tkr->clock),
- tkr->cycle_last, tkr->mask);
+ now += timekeeping_delta_to_ns(tkr,
+ clocksource_delta(
+ tkr->read(tkr->clock),
+ tkr->cycle_last,
+ tkr->mask));
} while (read_seqcount_retry(&tkf->seq, seq));
return now;
next prev parent reply other threads:[~2016-10-14 12:56 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20161014125514uscas1p2cd792639354106580734df022fbaba7a@uscas1p2.samsung.com>
2016-10-14 12:54 ` [PATCH 4.7 00/31] 4.7.8-stable review Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 01/31] powerpc/pseries: use pci_host_bridge.release_fn() to kfree(phb) Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 02/31] cxl: use pcibios_free_controller_deferred() when removing vPHBs Greg Kroah-Hartman
2016-10-14 12:54 ` Greg Kroah-Hartman [this message]
2016-10-14 12:54 ` [PATCH 4.7 04/31] usb: dwc3: fix Clear Stall EP command failure Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 05/31] ALSA: ali5451: Fix out-of-bound position reporting Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 06/31] ALSA: usb-audio: Extend DragonFly dB scale quirk to cover other variants Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 07/31] ALSA: usb-line6: use the same declaration as definition in header for MIDI manufacturer ID Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 08/31] mfd: rtsx_usb: Avoid setting ucr->current_sg.status Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 09/31] mfd: atmel-hlcdc: Do not sleep in atomic context Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 10/31] mfd: 88pm80x: Double shifting bug in suspend/resume Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 12/31] xen/x86: Update topology map for PV VCPUs Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 13/31] KVM: PPC: Book3s PR: Allow access to unprivileged MMCR2 register Greg Kroah-Hartman
2016-10-14 12:54 ` [PATCH 4.7 15/31] KVM: arm64: Require in-kernel irqchip for PMU support Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 16/31] KVM: arm/arm64: vgic: Dont flush/sync without a working vgic Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 17/31] KVM: PPC: BookE: Fix a sanity check Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 18/31] arm64: fix dump_backtrace/unwind_frame with NULL tsk Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 19/31] x86/boot: Fix kdump, cleanup aborted E820_PRAM max_pfn manipulation Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 20/31] x86/irq: Prevent force migration of irqs which are not in the vector domain Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 21/31] x86/pkeys: Make protection keys an "eager" feature Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 22/31] x86/apic: Get rid of apic_version[] array Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 23/31] arch/x86: Handle non enumerated CPU after physical hotplug Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 24/31] x86/mm/pkeys: Do not skip PKRU register if debug registers are not used Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 25/31] x86/dumpstack: Fix x86_32 kernel_stack_pointer() previous stack access Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 26/31] ARM: dts: mvebu: armada-390: add missing compatibility string and bracket Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 28/31] ARM: cpuidle: Fix error return code Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 29/31] ima: use file_dentry() Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 30/31] tpm: fix a race condition in tpm2_unseal_trusted() Greg Kroah-Hartman
2016-10-14 12:55 ` [PATCH 4.7 31/31] tpm_crb: fix crb_req_canceled behavior Greg Kroah-Hartman
2016-10-14 18:54 ` [PATCH 4.7 00/31] 4.7.8-stable review Shuah Khan
2016-10-14 19:17 ` Guenter Roeck
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