From: "Paul E. McKenney" <paulmck@kernel.org>
To: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Joel Fernandes <joel@joelfernandes.org>,
Oleg Nesterov <oleg@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Jonathan Corbet <corbet@lwn.net>,
Randy Dunlap <rdunlap@infradead.org>,
Logan Gunthorpe <logang@deltatee.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Kurt Schwemmer <kurt.schwemmer@microsemi.com>,
linux-pci@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Felipe Balbi <balbi@kernel.org>,
linux-usb@vger.kernel.org, Kalle Valo <kvalo@codeaurora.org>,
"David S. Miller" <davem@davemloft.net>,
linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
Darren Hart <dvhart@infradead.org>,
Andy Shevchenko <andy@infradead.org>,
platform-driver-x86@vger.kernel.org,
Zhang Rui <rui.zhang@intel.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
linux-pm@vger.kernel.org, Len Brown <lenb@kernel.org>,
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Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>,
Vincent Chen <deanbo422@gmail.com>, Guo Ren <guoren@kernel.org>,
linux-csky@vger.kernel.org, Brian Cain <bcain@codeaurora.org>,
linux-hexagon@vger.kernel.org, Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
linux-ia64@vger.kernel.org, Michal Simek <monstr@monstr.eu>,
Michael Ellerman <mpe@ellerman.id.au>,
Arnd Bergmann <arnd@arndb.de>, Geoff Levand <geoff@infradead.org>,
linuxppc-dev@lists.ozlabs.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: Documentation/locking/locktypes: Further clarifications and wordsmithing
Date: Wed, 25 Mar 2020 09:39:19 -0700 [thread overview]
Message-ID: <20200325163919.GU19865@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200325160212.oavrni7gmzudnczv@linutronix.de>
On Wed, Mar 25, 2020 at 05:02:12PM +0100, Sebastian Siewior wrote:
> On 2020-03-25 13:27:49 [+0100], Thomas Gleixner wrote:
> > The documentation of rw_semaphores is wrong as it claims that the non-owner
> > reader release is not supported by RT. That's just history biased memory
> > distortion.
> >
> > Split the 'Owner semantics' section up and add separate sections for
> > semaphore and rw_semaphore to reflect reality.
> >
> > Aside of that the following updates are done:
> >
> > - Add pseudo code to document the spinlock state preserving mechanism on
> > PREEMPT_RT
> >
> > - Wordsmith the bitspinlock and lock nesting sections
> >
> > Co-developed-by: Paul McKenney <paulmck@kernel.org>
> > Signed-off-by: Paul McKenney <paulmck@kernel.org>
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
> > --- a/Documentation/locking/locktypes.rst
> > +++ b/Documentation/locking/locktypes.rst
> …
> > +rw_semaphore
> > +============
> > +
> > +rw_semaphore is a multiple readers and single writer lock mechanism.
> > +
> > +On non-PREEMPT_RT kernels the implementation is fair, thus preventing
> > +writer starvation.
> > +
> > +rw_semaphore complies by default with the strict owner semantics, but there
> > +exist special-purpose interfaces that allow non-owner release for readers.
> > +These work independent of the kernel configuration.
>
> This reads funny, could be my English. "This works independent …" maybe?
The "These" refers to "interfaces", which is plural, so "These" rather
than "This". But yes, it is a bit awkward, because you have to skip
back past "readers", "release", and "non-owner" to find the implied
subject of that last sentence.
So how about this instead, making the implied subject explicit?
rw_semaphore complies by default with the strict owner semantics, but there
exist special-purpose interfaces that allow non-owner release for readers.
These interfaces work independent of the kernel configuration.
Thanx, Paul
next prev parent reply other threads:[~2020-03-25 16:39 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-21 11:25 [patch V3 00/20] Lock ordering documentation and annotation for lockdep Thomas Gleixner
2020-03-21 11:25 ` [patch V3 01/20] PCI/switchtec: Fix init_completion race condition with poll_wait() Thomas Gleixner
2020-03-21 11:25 ` [patch V3 02/20] pci/switchtec: Replace completion wait queue usage for poll Thomas Gleixner
2020-03-21 11:25 ` [patch V3 03/20] usb: gadget: Use completion interface instead of open coding it Thomas Gleixner
2020-03-25 8:37 ` Felipe Balbi
2020-03-27 12:14 ` Sebastian Siewior
2020-03-21 11:25 ` [patch V3 04/20] orinoco_usb: Use the regular completion interfaces Thomas Gleixner
2020-03-21 11:25 ` [patch V3 05/20] acpi: Remove header dependency Thomas Gleixner
2020-03-21 11:25 ` [patch V3 06/20] nds32: Remove mm.h from asm/uaccess.h Thomas Gleixner
2020-03-21 11:25 ` [patch V3 07/20] csky: " Thomas Gleixner
2020-03-21 11:25 ` [patch V3 08/20] hexagon: " Thomas Gleixner
2020-03-23 21:46 ` Brian Cain
2020-03-21 11:25 ` [patch V3 09/20] ia64: " Thomas Gleixner
2020-03-21 11:25 ` [patch V3 10/20] microblaze: " Thomas Gleixner
2020-03-21 11:25 ` [patch V3 11/20] rcuwait: Add @state argument to rcuwait_wait_event() Thomas Gleixner
2020-03-21 11:25 ` [patch V3 12/20] powerpc/ps3: Convert half completion to rcuwait Thomas Gleixner
2020-03-21 13:22 ` Thomas Gleixner
2020-03-27 19:14 ` Geoff Levand
2020-03-21 11:25 ` [patch V3 13/20] Documentation: Add lock ordering and nesting documentation Thomas Gleixner
2020-03-23 2:55 ` Paul E. McKenney
2020-03-24 23:13 ` Thomas Gleixner
2020-03-25 0:28 ` Paul E. McKenney
2020-03-25 12:27 ` Documentation/locking/locktypes: Further clarifications and wordsmithing Thomas Gleixner
2020-03-25 16:02 ` Sebastian Siewior
2020-03-25 16:39 ` Paul E. McKenney [this message]
2020-03-25 16:54 ` Sebastian Siewior
2020-03-25 16:58 ` [PATCH v2] Documentation/locking/locktypes: minor copy editor fixes Randy Dunlap
2020-03-26 2:40 ` Paul E. McKenney
2020-03-21 11:25 ` [patch V3 14/20] timekeeping: Split jiffies seqlock Thomas Gleixner
2020-03-21 11:25 ` [patch V3 15/20] sched/swait: Prepare usage in completions Thomas Gleixner
2020-03-21 11:26 ` [patch V3 16/20] completion: Use simple wait queues Thomas Gleixner
2020-03-23 15:20 ` [PATCH] completion: Use lockdep_assert_RT_in_threaded_ctx() in complete_all() Sebastian Siewior
2020-03-21 11:26 ` [patch V3 17/20] lockdep: Introduce wait-type checks Thomas Gleixner
2020-03-21 11:26 ` [patch V3 18/20] lockdep: Add hrtimer context tracing bits Thomas Gleixner
2020-03-21 11:26 ` [patch V3 19/20] lockdep: Annotate irq_work Thomas Gleixner
2020-03-21 11:26 ` [patch V3 20/20] lockdep: Add posixtimer context tracing bits Thomas Gleixner
2020-03-21 17:19 ` [patch V3 00/20] Lock ordering documentation and annotation for lockdep Davidlohr Bueso
2020-03-21 17:45 ` Thomas Gleixner
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