| Message ID | 20220825092311.179-2-thunder.leizhen@huawei.com (mailing list archive) |
|---|---|
| State | Superseded |
| Commit | 4ac3b3d1a19943b1522c0b1d0895aefbb80ec294 |
| Headers | show |
| Series | rcu/nocb: Delete local variable 'need_rcu_nocb_mask' in rcu_init_nohz() | expand |
On Thu, Aug 25, 2022 at 05:23:11PM +0800, Zhen Lei wrote: > When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional > CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not > available now, due to 'rcu_nocbs' is not specified. Check and initialize > 'rcu_nocb_mask' before using it. This code simplification strictly follows > this logic, compared with old implementations, unnecessary crossovers are > avoided and easy to understand. > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Much nicer, thank you! As usual, I could not resist the urge to wordsmith. Could you please check to make sure that I did not mess anything up? Thanx, Paul ------------------------------------------------------------------------ commit 4ac3b3d1a19943b1522c0b1d0895aefbb80ec294 Author: Zhen Lei <thunder.leizhen@huawei.com> Date: Thu Aug 25 17:23:11 2022 +0800 rcu: Simplify rcu_init_nohz() cpumask handling 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_nocb_mask= 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> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 0a5f0ef414845..c8167be2288fa 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1210,45 +1210,31 @@ 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; + const struct cpumask *cpumask = NULL; #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) */ - -#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) */ + cpumask = cpu_possible_mask; +#elif defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) + cpumask = tick_nohz_full_mask; +#endif - 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,
On Thu, Aug 25, 2022 at 10:26:54AM -0700, Paul E. McKenney wrote: > On Thu, Aug 25, 2022 at 05:23:11PM +0800, Zhen Lei wrote: > > When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional > > CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not > > available now, due to 'rcu_nocbs' is not specified. Check and initialize > > 'rcu_nocb_mask' before using it. This code simplification strictly follows > > this logic, compared with old implementations, unnecessary crossovers are > > avoided and easy to understand. > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > Much nicer, thank you! > > As usual, I could not resist the urge to wordsmith. Could you please > check to make sure that I did not mess anything up? > > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 4ac3b3d1a19943b1522c0b1d0895aefbb80ec294 > Author: Zhen Lei <thunder.leizhen@huawei.com> > Date: Thu Aug 25 17:23:11 2022 +0800 > > rcu: Simplify rcu_init_nohz() cpumask handling > > 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_nocb_mask= 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> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> thanks, - Joel > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index 0a5f0ef414845..c8167be2288fa 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -1210,45 +1210,31 @@ 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; > + const struct cpumask *cpumask = NULL; > > #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) */ > - > -#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) */ > + cpumask = cpu_possible_mask; > +#elif defined(CONFIG_NO_HZ_FULL) > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > + cpumask = tick_nohz_full_mask; > +#endif > > - 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,
On Thu, Aug 25, 2022 at 07:24:05PM +0000, Joel Fernandes wrote: > On Thu, Aug 25, 2022 at 10:26:54AM -0700, Paul E. McKenney wrote: > > On Thu, Aug 25, 2022 at 05:23:11PM +0800, Zhen Lei wrote: > > > When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional > > > CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not > > > available now, due to 'rcu_nocbs' is not specified. Check and initialize > > > 'rcu_nocb_mask' before using it. This code simplification strictly follows > > > this logic, compared with old implementations, unnecessary crossovers are > > > avoided and easy to understand. > > > > > > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > > > Much nicer, thank you! > > > > As usual, I could not resist the urge to wordsmith. Could you please > > check to make sure that I did not mess anything up? > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 4ac3b3d1a19943b1522c0b1d0895aefbb80ec294 > > Author: Zhen Lei <thunder.leizhen@huawei.com> > > Date: Thu Aug 25 17:23:11 2022 +0800 > > > > rcu: Simplify rcu_init_nohz() cpumask handling > > > > 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_nocb_mask= 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> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Thank you, and I will apply this on the next rebase. Thanx, Paul > thanks, > > - Joel > > > > > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > > index 0a5f0ef414845..c8167be2288fa 100644 > > --- a/kernel/rcu/tree_nocb.h > > +++ b/kernel/rcu/tree_nocb.h > > @@ -1210,45 +1210,31 @@ 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; > > + const struct cpumask *cpumask = NULL; > > > > #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) */ > > - > > -#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) */ > > + cpumask = cpu_possible_mask; > > +#elif defined(CONFIG_NO_HZ_FULL) > > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > > + cpumask = tick_nohz_full_mask; > > +#endif > > > > - 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,
On 2022/8/26 1:26, Paul E. McKenney wrote: > On Thu, Aug 25, 2022 at 05:23:11PM +0800, Zhen Lei wrote: >> When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional >> CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not >> available now, due to 'rcu_nocbs' is not specified. Check and initialize >> 'rcu_nocb_mask' before using it. This code simplification strictly follows >> this logic, compared with old implementations, unnecessary crossovers are >> avoided and easy to understand. >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > Much nicer, thank you! > > As usual, I could not resist the urge to wordsmith. Could you please > check to make sure that I did not mess anything up? Okay, thank you very much. The boot option name "rcu_nocb_mask=" is incorrect, should be "rcu_nocbs=". > > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 4ac3b3d1a19943b1522c0b1d0895aefbb80ec294 > Author: Zhen Lei <thunder.leizhen@huawei.com> > Date: Thu Aug 25 17:23:11 2022 +0800 > > rcu: Simplify rcu_init_nohz() cpumask handling > > 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_nocb_mask= will not have rcu_nocb_mask= ----> rcu_nocbs= > 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> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index 0a5f0ef414845..c8167be2288fa 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -1210,45 +1210,31 @@ 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; > + const struct cpumask *cpumask = NULL; > > #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) */ > - > -#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) */ > + cpumask = cpu_possible_mask; > +#elif defined(CONFIG_NO_HZ_FULL) > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > + cpumask = tick_nohz_full_mask; > +#endif > > - 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, > . >
On Fri, Aug 26, 2022 at 09:42:11AM +0800, Leizhen (ThunderTown) wrote: > > > On 2022/8/26 1:26, Paul E. McKenney wrote: > > On Thu, Aug 25, 2022 at 05:23:11PM +0800, Zhen Lei wrote: > >> When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional > >> CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not > >> available now, due to 'rcu_nocbs' is not specified. Check and initialize > >> 'rcu_nocb_mask' before using it. This code simplification strictly follows > >> this logic, compared with old implementations, unnecessary crossovers are > >> avoided and easy to understand. > >> > >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > > > > Much nicer, thank you! > > > > As usual, I could not resist the urge to wordsmith. Could you please > > check to make sure that I did not mess anything up? > > Okay, thank you very much. The boot option name "rcu_nocb_mask=" is > incorrect, should be "rcu_nocbs=". Good eyes, thank you! I will fix this on the next rebase. Thanx, Paul > > ------------------------------------------------------------------------ > > > > commit 4ac3b3d1a19943b1522c0b1d0895aefbb80ec294 > > Author: Zhen Lei <thunder.leizhen@huawei.com> > > Date: Thu Aug 25 17:23:11 2022 +0800 > > > > rcu: Simplify rcu_init_nohz() cpumask handling > > > > 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_nocb_mask= will not have > > rcu_nocb_mask= ----> rcu_nocbs= > > > 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> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > > index 0a5f0ef414845..c8167be2288fa 100644 > > --- a/kernel/rcu/tree_nocb.h > > +++ b/kernel/rcu/tree_nocb.h > > @@ -1210,45 +1210,31 @@ 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; > > + const struct cpumask *cpumask = NULL; > > > > #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) */ > > - > > -#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) */ > > + cpumask = cpu_possible_mask; > > +#elif defined(CONFIG_NO_HZ_FULL) > > + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) > > + cpumask = tick_nohz_full_mask; > > +#endif > > > > - 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, > > . > > > > -- > Regards, > Zhen Lei
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 0a5f0ef41484518..c8167be2288fa2c 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1210,45 +1210,31 @@ 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; + const struct cpumask *cpumask = NULL; #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) */ - -#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) */ + cpumask = cpu_possible_mask; +#elif defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) + cpumask = tick_nohz_full_mask; +#endif - 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,
When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not available now, due to 'rcu_nocbs' is not specified. Check and initialize 'rcu_nocb_mask' before using it. This code simplification strictly follows this logic, compared with old implementations, unnecessary crossovers are avoided and easy to understand. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- kernel/rcu/tree_nocb.h | 32 +++++++++----------------------- 1 file changed, 9 insertions(+), 23 deletions(-)