[PATCH tip/core/rcu 3/6] documentation: Update NO_HZ_FULL interaction with POSIX timers

From: Paul E. McKenney
Date: Tue Mar 03 2015 - 11:38:01 EST


From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxx>
---
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

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