Messages in this thread | | | From | Yury Norov <> | Date | Tue, 26 Jan 2021 13:36:23 -0800 | Subject | Re: [PATCH 8/8] rcu: deprecate "all" option to rcu_nocbs= |
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On Tue, Jan 26, 2021 at 9:12 AM Paul Gortmaker <paul.gortmaker@windriver.com> wrote: > > With the core bitmap support now accepting "N" as a placeholder for > the end of the bitmap, "all" can be represented as "0-N" and has the > advantage of not being specific to RCU (or any other subsystem). > > So deprecate the use of "all" by removing documentation references > to it. The support itself needs to remain for now, since we don't > know how many people out there are using it currently, but since it > is in an __init area anyway, it isn't worth losing sleep over. > > Cc: Yury Norov <yury.norov@gmail.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: "Paul E. McKenney" <paulmck@kernel.org> > Cc: Josh Triplett <josh@joshtriplett.org> > Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> > --- > Documentation/admin-guide/kernel-parameters.txt | 4 +--- > kernel/rcu/tree_plugin.h | 6 ++---- > 2 files changed, 3 insertions(+), 7 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index a10b545c2070..a116c0ff0a91 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4037,9 +4037,7 @@ > see CONFIG_RAS_CEC help text. > > rcu_nocbs= [KNL] > - The argument is a cpu list, as described above, > - except that the string "all" can be used to > - specify every CPU on the system. > + The argument is a cpu list, as described above. > > In kernels built with CONFIG_RCU_NOCB_CPU=y, set > the specified list of CPUs to be no-callback CPUs. > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index 7e291ce0a1d6..56788dfde922 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -1463,14 +1463,12 @@ static void rcu_cleanup_after_idle(void) > > /* > * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. > - * The string after the "rcu_nocbs=" is either "all" for all CPUs, or a > - * comma-separated list of CPUs and/or CPU ranges. If an invalid list is > - * given, a warning is emitted and all CPUs are offloaded. > + * If the list is invalid, a warning is emitted and all CPUs are offloaded. > */ > static int __init rcu_nocb_setup(char *str) > { > alloc_bootmem_cpumask_var(&rcu_nocb_mask); > - if (!strcasecmp(str, "all")) > + if (!strcasecmp(str, "all")) /* legacy: use "0-N" instead */
I think 'all' and 'none' is a good idea. It's simple and convenient. But if you don't like it, can you please at least put this comment in system log using WARN_ON_ONCE(). It's quite possible that Linux users don't read source code comments.
> cpumask_setall(rcu_nocb_mask); > else > if (cpulist_parse(str, rcu_nocb_mask)) { > -- > 2.17.1 >
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