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rcu: Introduce CONFIG_RCU_EXP_CPU_STALL_TIMEOUT

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Currently both expedited and regular grace period stall warnings use
a single timeout value that with units of seconds.  However, recent
Android use cases problem require a sub-100-millisecond expedited RCU CPU
stall warning.  Given that expedited RCU grace periods normally complete
in far less than a single millisecond, especially for small systems,
this is not unreasonable.

Therefore introduce the CONFIG_RCU_EXP_CPU_STALL_TIMEOUT kernel
configuration that defaults to 20 msec on Android and remains the same
as that of the non-expedited stall warnings otherwise.  It also can be
changed in run-time via: /sys/.../parameters/rcu_exp_cpu_stall_timeout.

[ paulmck: Default of zero to use CONFIG_RCU_STALL_TIMEOUT. ]

Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Uladzislau Rezki
2022-02-16 14:52:09 +01:00
committed by Paul E. McKenney
parent 3123109284
commit 28b3ae4265
7 changed files with 80 additions and 2 deletions
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14
kernel/rcu/Kconfig.debug
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@@ -91,6 +91,20 @@ config RCU_CPU_STALL_TIMEOUT
RCU grace period persists, additional CPU stall warnings are
printed at more widely spaced intervals.
config RCU_EXP_CPU_STALL_TIMEOUT
int "Expedited RCU CPU stall timeout in milliseconds"
depends on RCU_STALL_COMMON
range 0 21000
default 20 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. 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"
depends on DEBUG_KERNEL