From: Frederic Weisbecker <frederic@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Tony Luck <tony.luck@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Vasily Gorbik <gor@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Heiko Carstens <hca@linux.ibm.com>
Subject: [RFC PATCH 0/4] irq: Reorder time handling against HARDIRQ_OFFSET on IRQ entry
Date: Wed, 25 Nov 2020 03:15:38 +0100 [thread overview]
Message-ID: <20201125021542.30237-1-frederic@kernel.org> (raw)
There are two issues with the current layout of tick_irq_enter() as
it's called before HARDIRQ_OFFSET is incremented:
1) It's not correctly handled by lockdep which doesn't consider it as
hardirq context. And jiffies/timekeeping update take a few interesting
locks.
2) Softirqs need to be explicitly disabled around it to prevent ksoftirqd
from being spuriously woken up.
The current call dependency prevents tick_irq_enter() from being moved
after HARDIRQ_OFFSET: account_irq_enter_time() needs to be called before
HARDIRQ_OFFSET incrementation due to cputime index dispatch and it must
be called after tick_irq_enter() which updates the clocks that may be
necessary for cputime accounting.
Here is a proposal to fix this layout.
(The EXPORT_SYMBOL_GPL() in vtime will likely disappear in the next take
as they don't seem to be necessary anymore, but I'll need to check
that thoroughly).
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
irq/core
HEAD: 9502ee20aed8bb847176e1d7d83ccd0625430744
Frederic Weisbecker (4):
sched/vtime: Consolidate IRQ time accounting
s390/vtime: Convert to consolidated IRQ time accounting
irqtime: Move irqtime entry accounting after irq offset incrementation
irq: Call tick_irq_enter() inside HARDIRQ_OFFSET
arch/ia64/kernel/time.c | 22 +++++++---
arch/powerpc/kernel/time.c | 60 ++++++++++++++++++++--------
arch/s390/include/asm/vtime.h | 1 -
arch/s390/kernel/vtime.c | 60 ++++++++++++++++++----------
include/linux/hardirq.h | 4 +-
include/linux/vtime.h | 18 ++++-----
kernel/sched/cputime.c | 75 +++++++++++++++++++++++++++--------
kernel/softirq.c | 16 +++-----
8 files changed, 176 insertions(+), 80 deletions(-)
--
2.25.1
next reply other threads:[~2020-11-25 2:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-25 2:15 Frederic Weisbecker [this message]
2020-11-25 2:15 ` [RFC PATCH 1/4] sched/vtime: Consolidate IRQ time accounting Frederic Weisbecker
2020-11-25 2:15 ` [RFC PATCH 2/4] s390/vtime: Convert to consolidated " Frederic Weisbecker
2020-11-25 2:15 ` [RFC PATCH 3/4] sched/irqtime: Move irqtime entry accounting after irq offset incrementation Frederic Weisbecker
2020-11-25 2:15 ` [RFC PATCH 4/4] irq: Call tick_irq_enter() inside HARDIRQ_OFFSET Frederic Weisbecker
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