[PATCH] s390: deadlock in appldata
The system might hang when using appldata_mem with high I/O traffic and a large number of devices. The spinlocks bdev_lock and swaplock are acquired via calls to si_meminfo() and si_swapinfo() from a tasklet, i.e. interrupt context, which can lead to a deadlock. Replace tasklet with work queue. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -28,6 +28,7 @@
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//#include <linux/kernel_stat.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/workqueue.h>
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#include "appldata.h"
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@ -133,9 +134,12 @@ static int appldata_interval = APPLDATA_CPU_INTERVAL;
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static int appldata_timer_active;
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/*
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* Tasklet
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* Work queue
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*/
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static struct tasklet_struct appldata_tasklet_struct;
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static struct workqueue_struct *appldata_wq;
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static void appldata_work_fn(void *data);
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static DECLARE_WORK(appldata_work, appldata_work_fn, NULL);
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/*
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* Ops list
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@ -144,11 +148,11 @@ static DEFINE_SPINLOCK(appldata_ops_lock);
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static LIST_HEAD(appldata_ops_list);
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/************************* timer, tasklet, DIAG ******************************/
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/*************************** timer, work, DIAG *******************************/
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/*
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* appldata_timer_function()
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*
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* schedule tasklet and reschedule timer
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* schedule work and reschedule timer
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*/
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static void appldata_timer_function(unsigned long data, struct pt_regs *regs)
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{
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@ -157,22 +161,22 @@ static void appldata_timer_function(unsigned long data, struct pt_regs *regs)
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atomic_read(&appldata_expire_count));
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if (atomic_dec_and_test(&appldata_expire_count)) {
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atomic_set(&appldata_expire_count, num_online_cpus());
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tasklet_schedule((struct tasklet_struct *) data);
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queue_work(appldata_wq, (struct work_struct *) data);
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}
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}
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/*
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* appldata_tasklet_function()
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* appldata_work_fn()
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*
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* call data gathering function for each (active) module
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*/
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static void appldata_tasklet_function(unsigned long data)
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static void appldata_work_fn(void *data)
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{
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struct list_head *lh;
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struct appldata_ops *ops;
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int i;
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P_DEBUG(" -= Tasklet =-\n");
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P_DEBUG(" -= Work Queue =-\n");
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i = 0;
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spin_lock(&appldata_ops_lock);
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list_for_each(lh, &appldata_ops_list) {
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@ -231,7 +235,7 @@ static int appldata_diag(char record_nr, u16 function, unsigned long buffer,
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: "=d" (ry) : "d" (&(appldata_parameter_list)) : "cc");
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return (int) ry;
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}
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/********************** timer, tasklet, DIAG <END> ***************************/
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/************************ timer, work, DIAG <END> ****************************/
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/****************************** /proc stuff **********************************/
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@ -411,7 +415,7 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
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struct list_head *lh;
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found = 0;
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spin_lock_bh(&appldata_ops_lock);
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spin_lock(&appldata_ops_lock);
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list_for_each(lh, &appldata_ops_list) {
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tmp_ops = list_entry(lh, struct appldata_ops, list);
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if (&tmp_ops->ctl_table[2] == ctl) {
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@ -419,15 +423,15 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
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}
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}
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if (!found) {
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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return -ENODEV;
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}
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ops = ctl->data;
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if (!try_module_get(ops->owner)) { // protect this function
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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return -ENODEV;
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}
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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if (!*lenp || *ppos) {
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*lenp = 0;
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@ -451,10 +455,11 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
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return -EFAULT;
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}
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spin_lock_bh(&appldata_ops_lock);
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spin_lock(&appldata_ops_lock);
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if ((buf[0] == '1') && (ops->active == 0)) {
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if (!try_module_get(ops->owner)) { // protect tasklet
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spin_unlock_bh(&appldata_ops_lock);
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// protect work queue callback
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if (!try_module_get(ops->owner)) {
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spin_unlock(&appldata_ops_lock);
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module_put(ops->owner);
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return -ENODEV;
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}
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@ -485,7 +490,7 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
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}
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module_put(ops->owner);
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}
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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out:
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*lenp = len;
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*ppos += len;
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@ -529,7 +534,7 @@ int appldata_register_ops(struct appldata_ops *ops)
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}
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memset(ops->ctl_table, 0, 4*sizeof(struct ctl_table));
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spin_lock_bh(&appldata_ops_lock);
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spin_lock(&appldata_ops_lock);
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list_for_each(lh, &appldata_ops_list) {
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tmp_ops = list_entry(lh, struct appldata_ops, list);
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P_DEBUG("register_ops loop: %i) name = %s, ctl = %i\n",
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@ -541,18 +546,18 @@ int appldata_register_ops(struct appldata_ops *ops)
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APPLDATA_PROC_NAME_LENGTH) == 0) {
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P_ERROR("Name \"%s\" already registered!\n", ops->name);
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kfree(ops->ctl_table);
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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return -EBUSY;
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}
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if (tmp_ops->ctl_nr == ops->ctl_nr) {
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P_ERROR("ctl_nr %i already registered!\n", ops->ctl_nr);
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kfree(ops->ctl_table);
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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return -EBUSY;
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}
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}
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list_add(&ops->list, &appldata_ops_list);
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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ops->ctl_table[0].ctl_name = CTL_APPLDATA;
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ops->ctl_table[0].procname = appldata_proc_name;
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@ -583,12 +588,12 @@ int appldata_register_ops(struct appldata_ops *ops)
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*/
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void appldata_unregister_ops(struct appldata_ops *ops)
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{
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spin_lock_bh(&appldata_ops_lock);
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spin_lock(&appldata_ops_lock);
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unregister_sysctl_table(ops->sysctl_header);
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list_del(&ops->list);
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kfree(ops->ctl_table);
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ops->ctl_table = NULL;
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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P_INFO("%s-ops unregistered!\n", ops->name);
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}
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/********************** module-ops management <END> **************************/
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@ -602,7 +607,7 @@ appldata_online_cpu(int cpu)
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init_virt_timer(&per_cpu(appldata_timer, cpu));
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per_cpu(appldata_timer, cpu).function = appldata_timer_function;
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per_cpu(appldata_timer, cpu).data = (unsigned long)
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&appldata_tasklet_struct;
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&appldata_work;
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atomic_inc(&appldata_expire_count);
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spin_lock(&appldata_timer_lock);
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__appldata_vtimer_setup(APPLDATA_MOD_TIMER);
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@ -615,7 +620,7 @@ appldata_offline_cpu(int cpu)
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del_virt_timer(&per_cpu(appldata_timer, cpu));
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if (atomic_dec_and_test(&appldata_expire_count)) {
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atomic_set(&appldata_expire_count, num_online_cpus());
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tasklet_schedule(&appldata_tasklet_struct);
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queue_work(appldata_wq, &appldata_work);
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}
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spin_lock(&appldata_timer_lock);
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__appldata_vtimer_setup(APPLDATA_MOD_TIMER);
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@ -648,7 +653,7 @@ static struct notifier_block __devinitdata appldata_nb = {
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/*
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* appldata_init()
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*
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* init timer and tasklet, register /proc entries
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* init timer, register /proc entries
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*/
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static int __init appldata_init(void)
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{
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@ -657,6 +662,12 @@ static int __init appldata_init(void)
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P_DEBUG("sizeof(parameter_list) = %lu\n",
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sizeof(struct appldata_parameter_list));
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appldata_wq = create_singlethread_workqueue("appldata");
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if (!appldata_wq) {
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P_ERROR("Could not create work queue\n");
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return -ENOMEM;
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}
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for_each_online_cpu(i)
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appldata_online_cpu(i);
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@ -670,7 +681,6 @@ static int __init appldata_init(void)
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appldata_table[1].de->owner = THIS_MODULE;
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#endif
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tasklet_init(&appldata_tasklet_struct, appldata_tasklet_function, 0);
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P_DEBUG("Base interface initialized.\n");
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return 0;
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}
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@ -678,7 +688,7 @@ static int __init appldata_init(void)
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/*
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* appldata_exit()
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*
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* stop timer and tasklet, unregister /proc entries
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* stop timer, unregister /proc entries
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*/
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static void __exit appldata_exit(void)
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{
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@ -690,7 +700,7 @@ static void __exit appldata_exit(void)
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/*
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* ops list should be empty, but just in case something went wrong...
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*/
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spin_lock_bh(&appldata_ops_lock);
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spin_lock(&appldata_ops_lock);
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list_for_each(lh, &appldata_ops_list) {
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ops = list_entry(lh, struct appldata_ops, list);
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rc = appldata_diag(ops->record_nr, APPLDATA_STOP_REC,
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@ -700,7 +710,7 @@ static void __exit appldata_exit(void)
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"return code: %d\n", ops->name, rc);
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}
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}
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spin_unlock_bh(&appldata_ops_lock);
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spin_unlock(&appldata_ops_lock);
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for_each_online_cpu(i)
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appldata_offline_cpu(i);
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@ -709,7 +719,7 @@ static void __exit appldata_exit(void)
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unregister_sysctl_table(appldata_sysctl_header);
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tasklet_kill(&appldata_tasklet_struct);
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destroy_workqueue(appldata_wq);
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P_DEBUG("... module unloaded!\n");
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}
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/**************************** init / exit <END> ******************************/
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@ -68,7 +68,7 @@ struct appldata_mem_data {
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u64 pgmajfault; /* page faults (major only) */
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// <-- New in 2.6
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} appldata_mem_data;
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} __attribute__((packed)) appldata_mem_data;
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static inline void appldata_debug_print(struct appldata_mem_data *mem_data)
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@ -57,7 +57,7 @@ struct appldata_net_sum_data {
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u64 rx_dropped; /* no space in linux buffers */
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u64 tx_dropped; /* no space available in linux */
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u64 collisions; /* collisions while transmitting */
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} appldata_net_sum_data;
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} __attribute__((packed)) appldata_net_sum_data;
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static inline void appldata_print_debug(struct appldata_net_sum_data *net_data)
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@ -49,7 +49,7 @@ struct appldata_os_per_cpu {
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u32 per_cpu_softirq; /* ... spent in softirqs */
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u32 per_cpu_iowait; /* ... spent while waiting for I/O */
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// <-- New in 2.6
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};
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} __attribute__((packed));
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struct appldata_os_data {
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u64 timestamp;
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@ -75,7 +75,7 @@ struct appldata_os_data {
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/* per cpu data */
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struct appldata_os_per_cpu os_cpu[0];
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};
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} __attribute__((packed));
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static struct appldata_os_data *appldata_os_data;
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