| Message ID | 20220913030036.1569-2-thunder.leizhen@huawei.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 2f9114670584a3ca0eacb8c08f05326854d891ce |
| Headers | show |
| Series | cu/nocb: Delete local variable 'need_rcu_nocb_mask' in rcu_init_nohz() | expand |
On Tue, Sep 13, 2022 at 11:00:36AM +0800, Zhen Lei wrote: > In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or > CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. > Except that kernels booted without the rcu_nocbs= will not have > allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses > its need_rcu_nocb_mask and offload_all local variables to track the > rcu_nocb and nohz_full state. > > But there is a much simpler approach, namely creating a cpumask pointer > to track the default and then using cpumask_available() to check the > rcu_nocb_mask state. This commit takes this approach, thereby simplifying > and shortening the rcu_init_nohz() function. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> > Acked-by: Frederic Weisbecker <frederic@kernel.org> Looks good, thanks!
On Wed, Sep 14, 2022 at 12:46:34PM +0200, Frederic Weisbecker wrote: > On Tue, Sep 13, 2022 at 11:00:36AM +0800, Zhen Lei wrote: > > In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or > > CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. > > Except that kernels booted without the rcu_nocbs= will not have > > allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses > > its need_rcu_nocb_mask and offload_all local variables to track the > > rcu_nocb and nohz_full state. > > > > But there is a much simpler approach, namely creating a cpumask pointer > > to track the default and then using cpumask_available() to check the > > rcu_nocb_mask state. This commit takes this approach, thereby simplifying > > and shortening the rcu_init_nohz() function. > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > Acked-by: Frederic Weisbecker <frederic@kernel.org> > > Looks good, thanks! Queued and pushed, thank you all! Thanx, Paul
On Wed, Sep 14, 2022 at 04:30:06AM -0700, Paul E. McKenney wrote: > On Wed, Sep 14, 2022 at 12:46:34PM +0200, Frederic Weisbecker wrote: > > On Tue, Sep 13, 2022 at 11:00:36AM +0800, Zhen Lei wrote: > > > In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or > > > CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. > > > Except that kernels booted without the rcu_nocbs= will not have > > > allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses > > > its need_rcu_nocb_mask and offload_all local variables to track the > > > rcu_nocb and nohz_full state. > > > > > > But there is a much simpler approach, namely creating a cpumask pointer > > > to track the default and then using cpumask_available() to check the > > > rcu_nocb_mask state. This commit takes this approach, thereby simplifying > > > and shortening the rcu_init_nohz() function. > > > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> > > > Acked-by: Frederic Weisbecker <frederic@kernel.org> > > > > Looks good, thanks! > > Queued and pushed, thank you all! And this time, actually queued the most recent version. Apologies for my confusion. Thanx, Paul
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 0a5f0ef41484518..ce526cc2791ca6c 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1210,45 +1210,33 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); void __init rcu_init_nohz(void) { int cpu; - bool need_rcu_nocb_mask = false; - bool offload_all = false; struct rcu_data *rdp; - -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) - if (!rcu_state.nocb_is_setup) { - need_rcu_nocb_mask = true; - offload_all = true; - } -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ + const struct cpumask *cpumask = NULL; #if defined(CONFIG_NO_HZ_FULL) - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { - need_rcu_nocb_mask = true; - offload_all = false; /* NO_HZ_FULL has its own mask. */ - } -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) + cpumask = tick_nohz_full_mask; +#endif + + if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) && + !rcu_state.nocb_is_setup && !cpumask) + cpumask = cpu_possible_mask; - if (need_rcu_nocb_mask) { + if (cpumask) { if (!cpumask_available(rcu_nocb_mask)) { if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); return; } } + + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); rcu_state.nocb_is_setup = true; } if (!rcu_state.nocb_is_setup) return; -#if defined(CONFIG_NO_HZ_FULL) - if (tick_nohz_full_running) - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ - - if (offload_all) - cpumask_setall(rcu_nocb_mask); - if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); cpumask_and(rcu_nocb_mask, cpu_possible_mask,