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From: Cyril Bur <cyrilbur@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: mpe@ellerman.id.au, drjones@redhat.com, dzickus@redhat.com,
	akpm@linux-foundation.org, mingo@kernel.org, uobergfe@redhat.com,
	chaiw.fnst@cn.fujitsu.com, fabf@skynet.be, atomlin@redhat.com,
	benzh@chromium.org, schwidefsky@de.ibm.com,
	Cyril Bur <cyrilbur@gmail.com>
Subject: [PATCH v2 0/2] Quieten softlockup detector on virtualised kernels
Date: Fri,  9 Jan 2015 14:34:36 +1100	[thread overview]
Message-ID: <1420774478-16760-1-git-send-email-cyrilbur@gmail.com> (raw)

When the hypervisor pauses a virtualised kernel the kernel will observe a jump
in timebase, this can cause spurious messages from the softlockup detector.

Whilst these messages are harmless, they are accompanied with a stack trace
which causes undue concern and more problematically the stack trace in the
guest has nothing to do with the observed problem and can only be misleading.

Futhermore, on POWER8 this is completely avoidable with the introduction of
the Virtual Time Base (VTB) register.

V2:
	Remove the export of running_clock
	Added #ifdef CONFIG_PPC_PSERIES and optimised the non lpar + vtb cases.
	Replaced the use of sched_clock_with local_clock it was used originally in
the softlockup detector.

Cyril Bur (2):
  Add another clock for use with the soft lockup watchdog.
  powerpc: add running_clock for powerpc to prevent spurious softlockup
    warnings

 arch/powerpc/kernel/time.c | 32 ++++++++++++++++++++++++++++++++
 include/linux/sched.h      |  1 +
 kernel/sched/clock.c       | 13 +++++++++++++
 kernel/watchdog.c          |  2 +-
 4 files changed, 47 insertions(+), 1 deletion(-)

-- 
1.9.1


             reply	other threads:[~2015-01-09  3:35 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-09  3:34 Cyril Bur [this message]
2015-01-09  3:34 ` [PATCH v2 1/2] Add another clock for use with the soft lockup watchdog Cyril Bur
2015-02-10  6:19   ` Chai Wen
2015-01-09  3:34 ` [PATCH v2 2/2] powerpc: add running_clock for powerpc to prevent spurious softlockup warnings Cyril Bur
2015-02-04 10:42   ` Paul Bolle
2015-02-05  4:08     ` Cyril Bur
2015-02-02  4:58 ` [PATCH v2 0/2] Quieten softlockup detector on virtualised kernels Cyril Bur
2015-02-02 23:08   ` Andrew Morton
2015-02-05 20:48 ` Don Zickus

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