Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH 3/5] workqueue: ensure attrs-changing be sequentially | Date | Mon, 11 May 2015 17:35:50 +0800 |
| |
Current modification to attrs via sysfs is not atomically.
Process A (change cpumask) | Process B (change numa affinity) wq_cpumask_store() | wq_sysfs_prep_attrs() | | apply_workqueue_attrs() apply_workqueue_attrs() |
It results that the Process B's operation is totally reverted without any notification.
This behavior is acceptable but it is sometimes unexpected. Sequential model on non-performance-sensitive operations is more popular and preferred. So this patch moves wq_sysfs_prep_attrs() into the protection under wq_pool_mutex to ensure attrs-changing be sequentially.
This patch is also a preparation patch for next patch which change the API of apply_workqueue_attrs().
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> --- kernel/workqueue.c | 110 +++++++++++++++++++++++++++++++++-------------------- 1 file changed, 69 insertions(+), 41 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index e7accc1..efd9a3a 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3646,24 +3646,25 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx) mutex_unlock(&ctx->wq->mutex); } -/** - * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue - * @wq: the target workqueue - * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs() - * - * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA - * machines, this function maps a separate pwq to each NUMA node with - * possibles CPUs in @attrs->cpumask so that work items are affine to the - * NUMA node it was issued on. Older pwqs are released as in-flight work - * items finish. Note that a work item which repeatedly requeues itself - * back-to-back will stay on its current pwq. - * - * Performs GFP_KERNEL allocations. - * - * Return: 0 on success and -errno on failure. - */ -int apply_workqueue_attrs(struct workqueue_struct *wq, - const struct workqueue_attrs *attrs) +static void apply_wqattrs_lock(void) +{ + /* + * CPUs should stay stable across pwq creations and installations. + * Pin CPUs, determine the target cpumask for each node and create + * pwqs accordingly. + */ + get_online_cpus(); + mutex_lock(&wq_pool_mutex); +} + +static void apply_wqattrs_unlock(void) +{ + mutex_unlock(&wq_pool_mutex); + put_online_cpus(); +} + +static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, + const struct workqueue_attrs *attrs) { struct apply_wqattrs_ctx *ctx; int ret = -ENOMEM; @@ -3676,14 +3677,6 @@ int apply_workqueue_attrs(struct workqueue_struct *wq, if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs))) return -EINVAL; - /* - * CPUs should stay stable across pwq creations and installations. - * Pin CPUs, determine the target cpumask for each node and create - * pwqs accordingly. - */ - get_online_cpus(); - mutex_lock(&wq_pool_mutex); - ctx = apply_wqattrs_prepare(wq, attrs); /* the ctx has been prepared successfully, let's commit it */ @@ -3694,8 +3687,33 @@ int apply_workqueue_attrs(struct workqueue_struct *wq, apply_wqattrs_cleanup(ctx); - mutex_unlock(&wq_pool_mutex); - put_online_cpus(); + return ret; +} + +/** + * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue + * @wq: the target workqueue + * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs() + * + * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA + * machines, this function maps a separate pwq to each NUMA node with + * possibles CPUs in @attrs->cpumask so that work items are affine to the + * NUMA node it was issued on. Older pwqs are released as in-flight work + * items finish. Note that a work item which repeatedly requeues itself + * back-to-back will stay on its current pwq. + * + * Performs GFP_KERNEL allocations. + * + * Return: 0 on success and -errno on failure. + */ +int apply_workqueue_attrs(struct workqueue_struct *wq, + const struct workqueue_attrs *attrs) +{ + int ret; + + apply_wqattrs_lock(); + ret = apply_workqueue_attrs_locked(wq, attrs); + apply_wqattrs_unlock(); return ret; } @@ -4784,10 +4802,9 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) return -ENOMEM; - get_online_cpus(); cpumask_and(cpumask, cpumask, cpu_possible_mask); if (!cpumask_empty(cpumask)) { - mutex_lock(&wq_pool_mutex); + apply_wqattrs_lock(); /* save the old wq_unbound_cpumask. */ cpumask_copy(saved_cpumask, wq_unbound_cpumask); @@ -4800,9 +4817,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) if (ret < 0) cpumask_copy(wq_unbound_cpumask, saved_cpumask); - mutex_unlock(&wq_pool_mutex); + apply_wqattrs_unlock(); } - put_online_cpus(); free_cpumask_var(saved_cpumask); return ret; @@ -4927,18 +4943,22 @@ static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr, { struct workqueue_struct *wq = dev_to_wq(dev); struct workqueue_attrs *attrs; - int ret; + int ret = -ENOMEM; + + apply_wqattrs_lock(); attrs = wq_sysfs_prep_attrs(wq); if (!attrs) - return -ENOMEM; + goto out_unlock; if (sscanf(buf, "%d", &attrs->nice) == 1 && attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE) - ret = apply_workqueue_attrs(wq, attrs); + ret = apply_workqueue_attrs_locked(wq, attrs); else ret = -EINVAL; +out_unlock: + apply_wqattrs_unlock(); free_workqueue_attrs(attrs); return ret ?: count; } @@ -4962,16 +4982,20 @@ static ssize_t wq_cpumask_store(struct device *dev, { struct workqueue_struct *wq = dev_to_wq(dev); struct workqueue_attrs *attrs; - int ret; + int ret = -ENOMEM; + + apply_wqattrs_lock(); attrs = wq_sysfs_prep_attrs(wq); if (!attrs) - return -ENOMEM; + goto out_unlock; ret = cpumask_parse(buf, attrs->cpumask); if (!ret) - ret = apply_workqueue_attrs(wq, attrs); + ret = apply_workqueue_attrs_locked(wq, attrs); +out_unlock: + apply_wqattrs_unlock(); free_workqueue_attrs(attrs); return ret ?: count; } @@ -4995,18 +5019,22 @@ static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr, { struct workqueue_struct *wq = dev_to_wq(dev); struct workqueue_attrs *attrs; - int v, ret; + int v, ret = -ENOMEM; + + apply_wqattrs_lock(); attrs = wq_sysfs_prep_attrs(wq); if (!attrs) - return -ENOMEM; + goto out_unlock; ret = -EINVAL; if (sscanf(buf, "%d", &v) == 1) { attrs->no_numa = !v; - ret = apply_workqueue_attrs(wq, attrs); + ret = apply_workqueue_attrs_locked(wq, attrs); } +out_unlock: + apply_wqattrs_unlock(); free_workqueue_attrs(attrs); return ret ?: count; } -- 2.1.0
| |