We call "anon workqueues" the set of unbound workqueues that don't carry the WQ_SYSFS flag.
They are a problem nowadays because people who work on CPU isolation (HPC, Real time, etc...) want to be able to migrate all the unbound workqueues away to a single housekeeping CPU. This control is possible through sysfs but only with WQ_SYSFS workqueues. Now we need to deal with the other unbound workqueues. There is two possible solutions: 1) Implement a sysfs directory for each unbound !WQ_SYSFS. This could be done with a specific Kconfig to make sure that these workqueue won't be considered as a stable ABI. But we all know that all distros will enable this Kconfig symbol and that a warning in the Kconfig help text won't protect against anything. 2) Implement a single sysfs directory containing only the cpumask file to the control the affinity of all the !WQ_SYSFS workqueues. This patch implements the second solution but only for non-ordered unbound workqueues. Ordered workqueues need a special treatment and will be handled in a subsequent patch. Cc: Christoph Lameter <[email protected]> Cc: Kevin Hilman <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Viresh Kumar <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- kernel/workqueue.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 117 insertions(+), 2 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 8749bef..2863c39 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -291,7 +291,8 @@ static bool wq_numa_enabled; /* unbound NUMA affinity enabled */ static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf; static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */ -static DEFINE_MUTEX(wq_unbound_mutex); /* protects list of unbound workqueues */ +/* protects list of unbound workqueues and wq_anon_cpumask*/ +static DEFINE_MUTEX(wq_unbound_mutex); static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */ static LIST_HEAD(workqueues); /* PL: list of all workqueues */ @@ -3313,13 +3314,127 @@ static struct device_attribute wq_sysfs_unbound_attrs[] = { __ATTR_NULL, }; +/* Protected by wq_anon_cpumask */ +static cpumask_t wq_anon_cpumask; +static ssize_t wq_anon_cpumask_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + int written; + + mutex_lock(&wq_unbound_mutex); + written = cpumask_scnprintf(buf, PAGE_SIZE, &wq_anon_cpumask); + mutex_unlock(&wq_unbound_mutex); + + written += scnprintf(buf + written, PAGE_SIZE - written, "\n"); + + return written; +} + +/* Must be called with wq_unbound_mutex held */ +static int wq_anon_cpumask_set(cpumask_var_t cpumask) +{ + struct workqueue_attrs *attrs; + struct workqueue_struct *wq; + int ret; + + list_for_each_entry(wq, &workqueues_unbound, unbound_list) { + /* WQ_SYSFS have their own directories */ + if (wq->flags & WQ_SYSFS) + continue; + /* Ordered workqueues need specific treatment */ + if (wq->flags & __WQ_ORDERED) + continue; + + attrs = wq_sysfs_prep_attrs(wq); + if (!attrs) + return -ENOMEM; + + cpumask_copy(attrs->cpumask, cpumask); + ret = apply_workqueue_attrs(wq, attrs); + free_workqueue_attrs(attrs); + if (ret) + break; + } + + return ret; +} + +static ssize_t wq_anon_cpumask_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + cpumask_var_t cpumask; + int ret = -EINVAL; + + if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL)) + return -ENOMEM; + + ret = cpumask_parse(buf, cpumask); + if (ret) + goto out; + + get_online_cpus(); + if (cpumask_intersects(cpumask, cpu_online_mask)) { + mutex_lock(&wq_unbound_mutex); + ret = wq_anon_cpumask_set(cpumask); + if (!ret) + cpumask_copy(&wq_anon_cpumask, cpumask); + mutex_unlock(&wq_unbound_mutex); + } + put_online_cpus(); +out: + free_cpumask_var(cpumask); + return ret ? ret : count; +} + +static void device_release(struct device *dev) +{ + kfree(dev); +} + +static struct device_attribute wq_sysfs_anon_attr = + __ATTR(cpumask, 0644, wq_anon_cpumask_show, wq_anon_cpumask_store); + static struct bus_type wq_subsys = { .name = "workqueue", }; static int __init wq_sysfs_init(void) { - return subsys_virtual_register(&wq_subsys, NULL); + struct device *anon_dev; + int ret; + + ret = subsys_virtual_register(&wq_subsys, NULL); + if (ret < 0) + return ret; + + mutex_lock(&wq_unbound_mutex); + cpumask_copy(&wq_anon_cpumask, cpu_possible_mask); + mutex_unlock(&wq_unbound_mutex); + + anon_dev = kzalloc(sizeof(*anon_dev), GFP_KERNEL); + if (!anon_dev) + return -ENOMEM; + + anon_dev->bus = &wq_subsys; + anon_dev->init_name = "anon_wqs"; + anon_dev->release = device_release; + + ret = device_register(anon_dev); + if (ret) { + kfree(anon_dev); + return ret; + } + + ret = device_create_file(anon_dev, &wq_sysfs_anon_attr); + if (ret) { + device_unregister(anon_dev); + return ret; + } + + kobject_uevent(&anon_dev->kobj, KOBJ_ADD); + + return 0; } core_initcall(wq_sysfs_init); -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
