From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: "Alan Stern" <stern@rowland.harvard.edu>,
"Will Deacon" <will.deacon@arm.com>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Andrea Parri" <parri.andrea@gmail.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
priyalee.kushwaha@intel.com,
"Stanisław Drozd" <drozdziak1@gmail.com>,
"Arnd Bergmann" <arnd@arndb.de>,
ldr709@gmail.com, "Thomas Gleixner" <tglx@linutronix.de>,
"Peter Zijlstra" <peterz@infradead.org>,
"Josh Triplett" <josh@joshtriplett.org>,
"Nicolas Pitre" <nico@linaro.org>,
"Krister Johansen" <kjlx@templeofstupid.com>,
"Vegard Nossum" <vegard.nossum@oracle.com>,
dcb314@hotmail.com, "Wu Fengguang" <fengguang.wu@intel.com>,
"Frederic Weisbecker" <fweisbec@gmail.com>,
"Rik van Riel" <riel@redhat.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ingo Molnar" <mingo@kernel.org>,
"Luc Maranget" <luc.maranget@inria.fr>,
"Jade Alglave" <j.alglave@ucl.ac.uk>
Subject: Re: [GIT PULL rcu/next] RCU commits for 4.13
Date: Fri, 30 Jun 2017 10:31:26 -0700 [thread overview]
Message-ID: <20170630173126.GZ2393@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170630051654.wsoog5nlwtmbh5y2@tardis>
On Fri, Jun 30, 2017 at 01:16:54PM +0800, Boqun Feng wrote:
> On Thu, Jun 29, 2017 at 09:02:41PM -0700, Paul E. McKenney wrote:
[ . . . ]
> > > > o kernel/task_work.c task_work_run()
> > > > Seems to rely on the acquire semantics only. This is to handle
> > >
> > > I think this one needs the stronger semantics, the smp_mb() is just
> > > hidden in the cmpxchg() before the raw_spin_unlock_wait() ;-)
> > >
> > > cmpxchg() sets a special value to indicate the task_work has been taken,
> > > and raw_spin_unlock_wait() must wait until the next critical section of
> > > ->pi_lock(in task_work_cancel()) could observe this, otherwise we may
> > > cancel a task_work while executing it.
> >
> > But either way, replacing the spin_unlock_wait() with a spin_lock()
> > immediately followed by a spin_unlock() should work correctly, right?
> >
>
> Yep ;-) I was thinking about the case that we kept spin_unlock_wait()
> with a simpler acquire semantics, and if so, we would actually have to
> do the replace. But I saw your patchset of removing it, so it doesn't
> matter.
Well, there is a fair amount of review and testing between now and
it getting in (assuming that it in fact does get in), but I do very
much appreciate the vote of confidence! ;-)
Thanx, Paul
next prev parent reply other threads:[~2017-06-30 17:31 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-12 21:37 [GIT PULL rcu/next] RCU commits for 4.13 Paul E. McKenney
2017-06-13 6:41 ` Ingo Molnar
2017-06-14 2:54 ` Andrea Parri
2017-06-14 4:33 ` Paul E. McKenney
2017-06-14 14:33 ` Andrea Parri
2017-06-14 20:23 ` Paul E. McKenney
2017-06-19 16:24 ` Andrea Parri
2017-06-27 20:58 ` Paul E. McKenney
2017-06-27 21:48 ` Linus Torvalds
2017-06-27 23:37 ` Paul E. McKenney
2017-06-28 15:31 ` Alan Stern
2017-06-28 17:03 ` Paul E. McKenney
2017-06-28 20:16 ` Alan Stern
2017-06-28 23:54 ` Paul E. McKenney
2017-06-29 0:05 ` Linus Torvalds
2017-06-29 0:45 ` Paul E. McKenney
2017-06-29 3:17 ` Boqun Feng
2017-06-29 18:47 ` Paul E. McKenney
2017-06-29 11:36 ` Will Deacon
2017-06-29 11:38 ` Will Deacon
2017-06-29 15:59 ` Alan Stern
2017-06-29 18:11 ` Paul E. McKenney
2017-06-30 2:51 ` Boqun Feng
2017-06-30 4:02 ` Paul E. McKenney
2017-06-30 5:16 ` Boqun Feng
2017-06-30 17:31 ` Paul E. McKenney [this message]
2017-06-29 18:46 ` Paul E. McKenney
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