Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / Documentation / RCU / NMI-RCU.txt

diff --git a/Documentation/RCU/NMI-RCU.txt b/Documentation/RCU/NMI-RCU.txt
index 687777f83b2371d4bd24e5d7abff88d7cf90a5d8..881353fd5bff1cbc1f3dead8009f5b86cb65832a 100644 (file)
--- a/Documentation/RCU/NMI-RCU.txt
+++ b/Documentation/RCU/NMI-RCU.txt
@@ -81,18 +81,19 @@ currently executing on some other CPU.  We therefore cannot free
 up any data structures used by the old NMI handler until execution
 of it completes on all other CPUs.
 
 up any data structures used by the old NMI handler until execution
 of it completes on all other CPUs.
 

-One way to accomplish this is via synchronize_sched(), perhaps as
+One way to accomplish this is via synchronize_rcu(), perhaps as

 follows:
 
        unset_nmi_callback();
 follows:
 
        unset_nmi_callback();

-       synchronize_sched();
+       synchronize_rcu();

        kfree(my_nmi_data);
 
        kfree(my_nmi_data);
 

-This works because synchronize_sched() blocks until all CPUs complete
-any preemption-disabled segments of code that they were executing.
-Since NMI handlers disable preemption, synchronize_sched() is guaranteed
+This works because (as of v4.20) synchronize_rcu() blocks until all
+CPUs complete any preemption-disabled segments of code that they were
+executing.
+Since NMI handlers disable preemption, synchronize_rcu() is guaranteed

 not to return until all ongoing NMI handlers exit.  It is therefore safe
 not to return until all ongoing NMI handlers exit.  It is therefore safe

-to free up the handler's data as soon as synchronize_sched() returns.
+to free up the handler's data as soon as synchronize_rcu() returns.

 
 Important note: for this to work, the architecture in question must
 invoke nmi_enter() and nmi_exit() on NMI entry and exit, respectively.
 
 Important note: for this to work, the architecture in question must
 invoke nmi_enter() and nmi_exit() on NMI entry and exit, respectively.