mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com,
	bobby.prani@gmail.com,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 3/6] documentation: Update NO_HZ_FULL interaction with POSIX timers
Date: Tue,  3 Mar 2015 08:37:37 -0800	[thread overview]
Message-ID: <1425400660-6380-3-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <1425400660-6380-1-git-send-email-paulmck@linux.vnet.ibm.com>

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

POSIX timers are no longer starved on adaptive-ticks CPUs.  Instead, they
prevent affected CPUs from entering adaptive-ticks mode.  This commit
therefore updates the NO_HZ.txt documentation.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/timers/NO_HZ.txt | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/Documentation/timers/NO_HZ.txt b/Documentation/timers/NO_HZ.txt
index cca122f25120..6eaf576294f3 100644
--- a/Documentation/timers/NO_HZ.txt
+++ b/Documentation/timers/NO_HZ.txt
@@ -158,13 +158,9 @@ not come for free:
 	to the need to inform kernel subsystems (such as RCU) about
 	the change in mode.
 
-3.	POSIX CPU timers on adaptive-tick CPUs may miss their deadlines
-	(perhaps indefinitely) because they currently rely on
-	scheduling-tick interrupts.  This will likely be fixed in
-	one of two ways: (1) Prevent CPUs with POSIX CPU timers from
-	entering adaptive-tick mode, or (2) Use hrtimers or other
-	adaptive-ticks-immune mechanism to cause the POSIX CPU timer to
-	fire properly.
+3.	POSIX CPU timers prevent CPUs from entering adaptive-tick mode.
+	Real-time applications needing to take actions based on CPU time
+	consumption need to use other means of doing so.
 
 4.	If there are more perf events pending than the hardware can
 	accommodate, they are normally round-robined so as to collect
-- 
1.8.1.5


  parent reply	other threads:[~2015-03-03 16:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-03 16:37 [PATCH tip/core/rcu 0/6] Documentation updates for 3.21^W4.1 Paul E. McKenney
2015-03-03 16:37 ` [PATCH tip/core/rcu 1/6] documentation: Update rcutree.kthread_prio for grace-period kthread use Paul E. McKenney
2015-03-03 16:37   ` [PATCH tip/core/rcu 2/6] documentation: Update based on on-demand vmstat workers Paul E. McKenney
2015-03-03 16:37   ` Paul E. McKenney [this message]
2015-03-03 16:37   ` [PATCH tip/core/rcu 4/6] documentation: Update per-CPU kthreads documentation Paul E. McKenney
2015-03-03 16:37   ` [PATCH tip/core/rcu 5/6] documentation: Clarify memory-barrier semantics of atomic operations Paul E. McKenney
2015-03-03 16:37   ` [PATCH tip/core/rcu 6/6] documentation: Clarify control-dependency pairing Paul E. McKenney

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=1425400660-6380-3-git-send-email-paulmck@linux.vnet.ibm.com \
    --to=paulmck@linux.vnet.ibm.com \
    --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=josh@joshtriplett.org \
    --cc=laijs@cn.fujitsu.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mathieu.desnoyers@efficios.com \
    --cc=mingo@kernel.org \
    --cc=oleg@redhat.com \
    --cc=peterz@infradead.org \
    --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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox

Powered by JetHome