On Tue, May 30, 2023 at 01:09:47PM -0700, Andrew Morton wrote: > On Tue, 30 May 2023 11:52:37 -0300 Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote: > > > Add a schedule_on_each_cpumask function, equivalent to > > schedule_on_each_cpu but accepting a cpumask to operate. > > > > Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> > > > > --- > > > > Index: linux-vmstat-remote/kernel/workqueue.c > > =================================================================== > > --- linux-vmstat-remote.orig/kernel/workqueue.c > > +++ linux-vmstat-remote/kernel/workqueue.c > > @@ -3455,6 +3455,56 @@ int schedule_on_each_cpu(work_func_t fun > > return 0; > > } > > > > + > > +/** > > + * schedule_on_each_cpumask - execute a function synchronously on each > > + * CPU in "cpumask", for those which are online. > > + * > > + * @func: the function to call > > + * @mask: the CPUs which to call function on > > + * > > + * schedule_on_each_cpu() executes @func on each specified CPU that is online, > > + * using the system workqueue and blocks until all such CPUs have completed. > > + * schedule_on_each_cpu() is very slow. > > + * > > + * Return: > > + * 0 on success, -errno on failure. > > + */ > > +int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask) > > +{ > > + int cpu; > > + struct work_struct __percpu *works; > > + cpumask_var_t effmask; > > + > > + works = alloc_percpu(struct work_struct); > > + if (!works) > > + return -ENOMEM; > > + > > + if (!alloc_cpumask_var(&effmask, GFP_KERNEL)) { > > + free_percpu(works); > > + return -ENOMEM; > > + } > > + > > + cpumask_and(effmask, cpumask, cpu_online_mask); > > + > > + cpus_read_lock(); > > + > > + for_each_cpu(cpu, effmask) { > > Should we check here that the cpu is still online? > > > + struct work_struct *work = per_cpu_ptr(works, cpu); > > + > > + INIT_WORK(work, func); > > + schedule_work_on(cpu, work); > > + } > > + > > + for_each_cpu(cpu, effmask) > > + flush_work(per_cpu_ptr(works, cpu)); > > + > > + cpus_read_unlock(); > > + free_percpu(works); > > + free_cpumask_var(effmask); > > + return 0; > > +} > > + > > /** > > * execute_in_process_context - reliably execute the routine with user context > > * @fn: the function to execute > > --- linux-vmstat-remote.orig/include/linux/workqueue.h > > +++ linux-vmstat-remote/include/linux/workqueue.h > > @@ -450,6 +450,7 @@ extern void __flush_workqueue(struct wor > > extern void drain_workqueue(struct workqueue_struct *wq); > > > > extern int schedule_on_each_cpu(work_func_t func); > > +extern int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask); > > May as well make schedule_on_each_cpu() call > schedule_on_each_cpumask()? Save a bit of text, and they're hardly > performance-critical to that extent. Agree, will wait for Michal's review before resending -v2. workqueue: add schedule_on_each_cpumask helper Add a schedule_on_each_cpumask function, equivalent to schedule_on_each_cpu but accepting a cpumask to operate. Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx> --- v2: - cpu_online_mask reference should happen with cpus_read_lock held (Andrew Morton) - have schedule_on_each_cpu call _cpumask variant (Andrew Morton) Index: linux-vmstat-remote/kernel/workqueue.c =================================================================== --- linux-vmstat-remote.orig/kernel/workqueue.c +++ linux-vmstat-remote/kernel/workqueue.c @@ -3431,27 +3431,56 @@ EXPORT_SYMBOL(cancel_delayed_work_sync); */ int schedule_on_each_cpu(work_func_t func) { + return schedule_on_each_cpumask(func, cpu_possible_mask); +} + + +/** + * schedule_on_each_cpumask - execute a function synchronously on each + * CPU in "cpumask", for those which are online. + * + * @func: the function to call + * @mask: the CPUs which to call function on + * + * schedule_on_each_cpu() executes @func on each specified CPU that is online, + * using the system workqueue and blocks until all such CPUs have completed. + * schedule_on_each_cpu() is very slow. + * + * Return: + * 0 on success, -errno on failure. + */ +int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask) +{ int cpu; struct work_struct __percpu *works; + cpumask_var_t effmask; works = alloc_percpu(struct work_struct); if (!works) return -ENOMEM; + if (!alloc_cpumask_var(&effmask, GFP_KERNEL)) { + free_percpu(works); + return -ENOMEM; + } + cpus_read_lock(); - for_each_online_cpu(cpu) { + cpumask_and(effmask, cpumask, cpu_online_mask); + + for_each_cpu(cpu, effmask) { struct work_struct *work = per_cpu_ptr(works, cpu); INIT_WORK(work, func); schedule_work_on(cpu, work); } - for_each_online_cpu(cpu) + for_each_cpu(cpu, effmask) flush_work(per_cpu_ptr(works, cpu)); cpus_read_unlock(); free_percpu(works); + free_cpumask_var(effmask); return 0; } Index: linux-vmstat-remote/include/linux/workqueue.h =================================================================== --- linux-vmstat-remote.orig/include/linux/workqueue.h +++ linux-vmstat-remote/include/linux/workqueue.h @@ -450,6 +450,7 @@ extern void __flush_workqueue(struct wor extern void drain_workqueue(struct workqueue_struct *wq); extern int schedule_on_each_cpu(work_func_t func); +extern int schedule_on_each_cpumask(work_func_t func, cpumask_t *cpumask); int execute_in_process_context(work_func_t fn, struct execute_work *);