From: Peter Zijlstra <peterz@infradead.org>
To: Josh Triplett <josh@joshtriplett.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com,
edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com,
oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH tip/core/rcu 6/7] rcu: Make expedited grace periods recheck dyntick idle state
Date: Mon, 14 Nov 2016 18:37:33 +0100 [thread overview]
Message-ID: <20161114173733.GJ3142@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20161114172512.bcwdy66elesds5t4@jtriplet-mobl2.jf.intel.com>
On Mon, Nov 14, 2016 at 09:25:12AM -0800, Josh Triplett wrote:
> On Mon, Nov 14, 2016 at 08:57:12AM -0800, Paul E. McKenney wrote:
> > Expedited grace periods check dyntick-idle state, and avoid sending
> > IPIs to idle CPUs, including those running guest OSes, and, on NOHZ_FULL
> > kernels, nohz_full CPUs. However, the kernel has been observed checking
> > a CPU while it was non-idle, but sending the IPI after it has gone
> > idle. This commit therefore rechecks idle state immediately before
> > sending the IPI, refraining from IPIing CPUs that have since gone idle.
> >
> > Reported-by: Rik van Riel <riel@redhat.com>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> atomic_add_return(0, ...) seems odd. Do you actually want that, rather
> than atomic_read(...)? If so, can you please document exactly why?
Yes that is weird. The only effective difference is that it would do a
load-exclusive instead of a regular load.
next prev parent reply other threads:[~2016-11-14 17:37 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-14 16:56 [PATCH tip/core/rcu 0/7] Miscellaneous fixes for 4.10 Paul E. McKenney
2016-11-14 16:57 ` [PATCH tip/core/rcu 1/7] rcu: Tighten up __call_rcu() rcu_head alignment check Paul E. McKenney
2016-11-14 16:57 ` [PATCH tip/core/rcu 2/7] rcu: Remove obsolete rcu_check_callbacks() header comment Paul E. McKenney
2016-11-14 16:57 ` [PATCH tip/core/rcu 3/7] rcu: Remove obsolete comment from __call_rcu() Paul E. McKenney
2016-11-14 16:57 ` [PATCH tip/core/rcu 4/7] rcu: RCU_TRACE enables event tracing as well as debugfs Paul E. McKenney
2016-11-14 16:57 ` [PATCH tip/core/rcu 5/7] torture: Trace long read-side delays Paul E. McKenney
2016-11-14 17:21 ` Josh Triplett
2016-11-14 18:44 ` Paul E. McKenney
2016-11-14 18:54 ` Josh Triplett
2016-11-14 16:57 ` [PATCH tip/core/rcu 6/7] rcu: Make expedited grace periods recheck dyntick idle state Paul E. McKenney
2016-11-14 17:25 ` Josh Triplett
2016-11-14 17:37 ` Peter Zijlstra [this message]
2016-11-14 18:12 ` Paul E. McKenney
2016-11-15 8:16 ` Peter Zijlstra
2016-11-15 14:36 ` Paul E. McKenney
2016-11-14 16:57 ` [PATCH tip/core/rcu 7/7] rcu: Don't kick unless grace period or request Paul E. McKenney
2016-11-14 17:26 ` [PATCH tip/core/rcu 0/7] Miscellaneous fixes for 4.10 Josh Triplett
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161114173733.GJ3142@twins.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=bobby.prani@gmail.com \
--cc=dhowells@redhat.com \
--cc=dipankar@in.ibm.com \
--cc=dvhart@linux.intel.com \
--cc=edumazet@google.com \
--cc=fweisbec@gmail.com \
--cc=jiangshanlai@gmail.com \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.