rcu: Remove conditional compilation for RCU CPU stall warnings

The RCU CPU stall warnings can now be controlled using the
rcu_cpu_stall_suppress boot-time parameter or via the same parameter
from sysfs.  There is therefore no longer any reason to have
kernel config parameters for this feature.  This commit therefore
removes the RCU_CPU_STALL_DETECTOR and RCU_CPU_STALL_DETECTOR_RUNNABLE
kernel config parameters.  The RCU_CPU_STALL_TIMEOUT parameter remains
to allow the timeout to be tuned and the RCU_CPU_STALL_VERBOSE parameter
remains to allow task-stall information to be suppressed if desired.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

2 files changed, 14 insertions, 11 deletions

diff --git a/Documentation/RCU/00-INDEX b/Documentation/RCU/00-INDEX
index 71b6f500ddb9..1d7a885761f5 100644
--- a/Documentation/RCU/00-INDEX
+++ b/Documentation/RCU/00-INDEX
@@ -21,7 +21,7 @@ rcu.txt
 RTFP.txt
         - List of RCU papers (bibliography) going back to 1980.
 stallwarn.txt
-        - RCU CPU stall warnings (CONFIG_RCU_CPU_STALL_DETECTOR)
+        - RCU CPU stall warnings (module parameter rcu_cpu_stall_suppress)
 torture.txt
         - RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
 trace.txt
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 862c08ef1fde..4e959208f736 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -1,22 +1,25 @@
 Using RCU's CPU Stall Detector
 
-The CONFIG_RCU_CPU_STALL_DETECTOR kernel config parameter enables
-RCU's CPU stall detector, which detects conditions that unduly delay
-RCU grace periods.  The stall detector's idea of what constitutes
-"unduly delayed" is controlled by a set of C preprocessor macros:
+The rcu_cpu_stall_suppress module parameter enables RCU's CPU stall
+detector, which detects conditions that unduly delay RCU grace periods.
+This module parameter enables CPU stall detection by default, but
+may be overridden via boot-time parameter or at runtime via sysfs.
+The stall detector's idea of what constitutes "unduly delayed" is
+controlled by a set of kernel configuration variables and cpp macros:
 
-RCU_SECONDS_TILL_STALL_CHECK
+CONFIG_RCU_CPU_STALL_TIMEOUT
 
-        This macro defines the period of time that RCU will wait from
-        the beginning of a grace period until it issues an RCU CPU
-        stall warning.  This time period is normally ten seconds.
+        This kernel configuration parameter defines the period of time
+        that RCU will wait from the beginning of a grace period until it
+        issues an RCU CPU stall warning.  This time period is normally
+        ten seconds.
 
 RCU_SECONDS_TILL_STALL_RECHECK
 
         This macro defines the period of time that RCU will wait after
         issuing a stall warning until it issues another stall warning
-        for the same stall.  This time period is normally set to thirty
-        seconds.
+        for the same stall.  This time period is normally set to three
+        times the check interval plus thirty seconds.
 
 RCU_STALL_RAT_DELAY