Hello, Paul.
Indeed the changed switched to 21 seconds. What is about just set the
60 000 for !ANDROID?
default 60000 if !ANDROID
On Mon, May 9, 2022 at 10:58 PM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> 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
--
Uladzislau Rezki
