Commit 911af505ef407c2511106c224dd640f882f0f590
Committed by
Paul E. McKenney
Paul E. McKenney
1 parent
34ed62461a
Exists in
smarc-l5.0.0_1.0.0-ga
and in
5 other branches
rcu: Provide compile-time control for no-CBs CPUs
Currently, the only way to specify no-CBs CPUs is via the rcu_nocbs kernel command-line parameter. This is inconvenient in some cases, particularly for randconfig testing, so this commit adds a new set of kernel configuration parameters. CONFIG_RCU_NOCB_CPU_NONE (the default) retains the old behavior, CONFIG_RCU_NOCB_CPU_ZERO offloads callback processing from CPU 0 (along with any other CPUs specified by the rcu_nocbs boot-time parameter), and CONFIG_RCU_NOCB_CPU_ALL offloads callback processing from all CPUs. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Showing 2 changed files with 53 additions and 0 deletions Side-by-side Diff
init/Kconfig
| ... | ... | @@ -676,6 +676,45 @@ |
| 676 | 676 | Say Y here if you want to help to debug reduced OS jitter. |
| 677 | 677 | Say N here if you are unsure. |
| 678 | 678 | |
| 679 | +choice | |
| 680 | + prompt "Build-forced no-CBs CPUs" | |
| 681 | + default RCU_NOCB_CPU_NONE | |
| 682 | + help | |
| 683 | + This option allows no-CBs CPUs to be specified at build time. | |
| 684 | + Additional no-CBs CPUs may be specified by the rcu_nocbs= | |
| 685 | + boot parameter. | |
| 686 | + | |
| 687 | +config RCU_NOCB_CPU_NONE | |
| 688 | + bool "No build_forced no-CBs CPUs" | |
| 689 | + depends on RCU_NOCB_CPU | |
| 690 | + help | |
| 691 | + This option does not force any of the CPUs to be no-CBs CPUs. | |
| 692 | + Only CPUs designated by the rcu_nocbs= boot parameter will be | |
| 693 | + no-CBs CPUs. | |
| 694 | + | |
| 695 | +config RCU_NOCB_CPU_ZERO | |
| 696 | + bool "CPU 0 is a build_forced no-CBs CPU" | |
| 697 | + depends on RCU_NOCB_CPU | |
| 698 | + help | |
| 699 | + This option forces CPU 0 to be a no-CBs CPU. Additional CPUs | |
| 700 | + may be designated as no-CBs CPUs using the rcu_nocbs= boot | |
| 701 | + parameter will be no-CBs CPUs. | |
| 702 | + | |
| 703 | + Select this if CPU 0 needs to be a no-CBs CPU for real-time | |
| 704 | + or energy-efficiency reasons. | |
| 705 | + | |
| 706 | +config RCU_NOCB_CPU_ALL | |
| 707 | + bool "All CPUs are build_forced no-CBs CPUs" | |
| 708 | + depends on RCU_NOCB_CPU | |
| 709 | + help | |
| 710 | + This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= | |
| 711 | + boot parameter will be ignored. | |
| 712 | + | |
| 713 | + Select this if all CPUs need to be no-CBs CPUs for real-time | |
| 714 | + or energy-efficiency reasons. | |
| 715 | + | |
| 716 | +endchoice | |
| 717 | + | |
| 679 | 718 | endmenu # "RCU Subsystem" |
| 680 | 719 | |
| 681 | 720 | config IKCONFIG |
kernel/rcutree_plugin.h
| ... | ... | @@ -85,6 +85,20 @@ |
| 85 | 85 | if (nr_cpu_ids != NR_CPUS) |
| 86 | 86 | printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); |
| 87 | 87 | #ifdef CONFIG_RCU_NOCB_CPU |
| 88 | +#ifndef CONFIG_RCU_NOCB_CPU_NONE | |
| 89 | + if (!have_rcu_nocb_mask) { | |
| 90 | + alloc_bootmem_cpumask_var(&rcu_nocb_mask); | |
| 91 | + have_rcu_nocb_mask = true; | |
| 92 | + } | |
| 93 | +#ifdef CONFIG_RCU_NOCB_CPU_ZERO | |
| 94 | + pr_info("\tExperimental no-CBs CPU 0\n"); | |
| 95 | + cpumask_set_cpu(0, rcu_nocb_mask); | |
| 96 | +#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ | |
| 97 | +#ifdef CONFIG_RCU_NOCB_CPU_ALL | |
| 98 | + pr_info("\tExperimental no-CBs for all CPUs\n"); | |
| 99 | + cpumask_setall(rcu_nocb_mask); | |
| 100 | +#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ | |
| 101 | +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ | |
| 88 | 102 | if (have_rcu_nocb_mask) { |
| 89 | 103 | cpulist_scnprintf(nocb_buf, sizeof(nocb_buf), rcu_nocb_mask); |
| 90 | 104 | pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf); |