Hello, Uladzislau,
And I wasn't paying attention when reviewing this patch:
084e1c049a8e ("rcu: Introduce CONFIG_RCU_EXP_CPU_STALL_TIMEOUT")
Distros specifying 60 seconds for the stall timeout get hit with a silent
change to 21 seconds for the expedited stall timeout.
Unless you tell me otherwise, I will merge the following diff into the
above commit. So please let me know if this will cause any problems.
Thanx, Paul
------------------------------------------------------------------------
diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst
index 1d863b04727c3..794837eb519b9 100644
--- a/Documentation/RCU/stallwarn.rst
+++ b/Documentation/RCU/stallwarn.rst
@@ -166,10 +166,12 @@ CONFIG_RCU_EXP_CPU_STALL_TIMEOUT
--------------------------------
Same as the CONFIG_RCU_CPU_STALL_TIMEOUT parameter but only for
- the expedited grace period. This parameter defines the period of
- time that RCU will wait from the beginning of an expedited grace
- period until it issues an RCU CPU stall warning. This time period
- is normally 20 milliseconds on Android devices.
+ the expedited grace period. This parameter defines the period
+ of time that RCU will wait from the beginning of an expedited
+ grace period until it issues an RCU CPU stall warning. This time
+ period is normally 20 milliseconds on Android devices. A zero
+ value causes the CONFIG_RCU_CPU_STALL_TIMEOUT value to be used,
+ after conversion to milliseconds.
This configuration parameter may be changed at runtime via the
/sys/module/rcupdate/parameters/rcu_exp_cpu_stall_timeout, however
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 34d44648f3f5d..ca9db809beda3 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4936,6 +4936,9 @@
and the maximum allowed value is 21000
milliseconds. Please note that this value is
adjusted to an arch timer tick resolution.
+ Setting this to zero causes the value from
+ rcupdate.rcu_cpu_stall_timeout to be used (after
+ conversion from seconds to milliseconds).
rcupdate.rcu_expedited= [KNL]
Use expedited grace-period primitives, for
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 39dd4b9d647f8..9b64e55d4f615 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -85,15 +85,16 @@ config RCU_CPU_STALL_TIMEOUT
config RCU_EXP_CPU_STALL_TIMEOUT
int "Expedited RCU CPU stall timeout in milliseconds"
depends on RCU_STALL_COMMON
- range 1 21000
+ range 0 21000
default 20 if ANDROID
- default 21000 if !ANDROID
-
+ default 0 if !ANDROID
help
If a given expedited RCU grace period extends more than the
specified number of milliseconds, a CPU stall warning is printed.
If the RCU grace period persists, additional CPU stall warnings
- are printed at more widely spaced intervals.
+ are printed at more widely spaced intervals. A value of zero
+ says to use the RCU_CPU_STALL_TIMEOUT value converted from
+ seconds to milliseconds.
config RCU_TRACE
bool "Enable tracing for RCU"
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 0a25a4ea6eef8..2464b0eccfd02 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -31,15 +31,17 @@ int rcu_exp_jiffies_till_stall_check(void)
int exp_stall_delay_delta = 0;
int till_stall_check;
- /*
- * Limit check must be consistent with the Kconfig limits for
- * CONFIG_RCU_EXP_CPU_STALL_TIMEOUT, so check the allowed range.
- * The minimum clamped value is "2UL", because at least one full
- * tick has to be guaranteed.
- */
+ // Zero says to use rcu_cpu_stall_timeout, but in milliseconds.
+ if (!cpu_stall_timeout)
+ cpu_stall_timeout = jiffies_to_msecs(rcu_jiffies_till_stall_check());
+
+ // Limit check must be consistent with the Kconfig limits for
+ // CONFIG_RCU_EXP_CPU_STALL_TIMEOUT, so check the allowed range.
+ // The minimum clamped value is "2UL", because at least one full
+ // tick has to be guaranteed.
till_stall_check = clamp(msecs_to_jiffies(cpu_stall_timeout), 2UL, 21UL * HZ);
- if (jiffies_to_msecs(till_stall_check) != cpu_stall_timeout)
+ if (cpu_stall_timeout && jiffies_to_msecs(till_stall_check) != cpu_stall_timeout)
WRITE_ONCE(rcu_exp_cpu_stall_timeout, jiffies_to_msecs(till_stall_check));
#ifdef CONFIG_PROVE_RCU
