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[PATCH] s390: deadlock in appldata
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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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Gerald Schaefer authored and Linus Torvalds committed Jun 5, 2005
1 parent 595bf2a commit f26d583
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Showing 4 changed files with 45 additions and 35 deletions.
72 changes: 41 additions & 31 deletions arch/s390/appldata/appldata_base.c
View file
Expand Up @@ -28,6 +28,7 @@
//#include <linux/kernel_stat.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/workqueue.h>

#include "appldata.h"

Expand Down Expand Up @@ -133,9 +134,12 @@ static int appldata_interval = APPLDATA_CPU_INTERVAL;
static int appldata_timer_active;

/*
* Tasklet
* Work queue
*/
static struct tasklet_struct appldata_tasklet_struct;
static struct workqueue_struct *appldata_wq;
static void appldata_work_fn(void *data);
static DECLARE_WORK(appldata_work, appldata_work_fn, NULL);


/*
* Ops list
Expand All @@ -144,11 +148,11 @@ static DEFINE_SPINLOCK(appldata_ops_lock);
static LIST_HEAD(appldata_ops_list);


/************************* timer, tasklet, DIAG ******************************/
/*************************** timer, work, DIAG *******************************/
/*
* appldata_timer_function()
*
* schedule tasklet and reschedule timer
* schedule work and reschedule timer
*/
static void appldata_timer_function(unsigned long data, struct pt_regs *regs)
{
Expand All @@ -157,22 +161,22 @@ static void appldata_timer_function(unsigned long data, struct pt_regs *regs)
atomic_read(&appldata_expire_count));
if (atomic_dec_and_test(&appldata_expire_count)) {
atomic_set(&appldata_expire_count, num_online_cpus());
tasklet_schedule((struct tasklet_struct *) data);
queue_work(appldata_wq, (struct work_struct *) data);
}
}

/*
* appldata_tasklet_function()
* appldata_work_fn()
*
* call data gathering function for each (active) module
*/
static void appldata_tasklet_function(unsigned long data)
static void appldata_work_fn(void *data)
{
struct list_head *lh;
struct appldata_ops *ops;
int i;

P_DEBUG(" -= Tasklet =-\n");
P_DEBUG(" -= Work Queue =-\n");
i = 0;
spin_lock(&appldata_ops_lock);
list_for_each(lh, &appldata_ops_list) {
Expand Down Expand Up @@ -231,7 +235,7 @@ static int appldata_diag(char record_nr, u16 function, unsigned long buffer,
: "=d" (ry) : "d" (&(appldata_parameter_list)) : "cc");
return (int) ry;
}
/********************** timer, tasklet, DIAG <END> ***************************/
/************************ timer, work, DIAG <END> ****************************/


/****************************** /proc stuff **********************************/
Expand Down Expand Up @@ -411,23 +415,23 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
struct list_head *lh;

found = 0;
spin_lock_bh(&appldata_ops_lock);
spin_lock(&appldata_ops_lock);
list_for_each(lh, &appldata_ops_list) {
tmp_ops = list_entry(lh, struct appldata_ops, list);
if (&tmp_ops->ctl_table[2] == ctl) {
found = 1;
}
}
if (!found) {
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);
return -ENODEV;
}
ops = ctl->data;
if (!try_module_get(ops->owner)) { // protect this function
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);
return -ENODEV;
}
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);

if (!*lenp || *ppos) {
*lenp = 0;
Expand All @@ -451,10 +455,11 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
return -EFAULT;
}

spin_lock_bh(&appldata_ops_lock);
spin_lock(&appldata_ops_lock);
if ((buf[0] == '1') && (ops->active == 0)) {
if (!try_module_get(ops->owner)) { // protect tasklet
spin_unlock_bh(&appldata_ops_lock);
// protect work queue callback
if (!try_module_get(ops->owner)) {
spin_unlock(&appldata_ops_lock);
module_put(ops->owner);
return -ENODEV;
}
Expand Down Expand Up @@ -485,7 +490,7 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
}
module_put(ops->owner);
}
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);
out:
*lenp = len;
*ppos += len;
Expand Down Expand Up @@ -529,7 +534,7 @@ int appldata_register_ops(struct appldata_ops *ops)
}
memset(ops->ctl_table, 0, 4*sizeof(struct ctl_table));

spin_lock_bh(&appldata_ops_lock);
spin_lock(&appldata_ops_lock);
list_for_each(lh, &appldata_ops_list) {
tmp_ops = list_entry(lh, struct appldata_ops, list);
P_DEBUG("register_ops loop: %i) name = %s, ctl = %i\n",
Expand All @@ -541,18 +546,18 @@ int appldata_register_ops(struct appldata_ops *ops)
APPLDATA_PROC_NAME_LENGTH) == 0) {
P_ERROR("Name \"%s\" already registered!\n", ops->name);
kfree(ops->ctl_table);
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);
return -EBUSY;
}
if (tmp_ops->ctl_nr == ops->ctl_nr) {
P_ERROR("ctl_nr %i already registered!\n", ops->ctl_nr);
kfree(ops->ctl_table);
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);
return -EBUSY;
}
}
list_add(&ops->list, &appldata_ops_list);
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);

ops->ctl_table[0].ctl_name = CTL_APPLDATA;
ops->ctl_table[0].procname = appldata_proc_name;
Expand Down Expand Up @@ -583,12 +588,12 @@ int appldata_register_ops(struct appldata_ops *ops)
*/
void appldata_unregister_ops(struct appldata_ops *ops)
{
spin_lock_bh(&appldata_ops_lock);
spin_lock(&appldata_ops_lock);
unregister_sysctl_table(ops->sysctl_header);
list_del(&ops->list);
kfree(ops->ctl_table);
ops->ctl_table = NULL;
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);
P_INFO("%s-ops unregistered!\n", ops->name);
}
/********************** module-ops management <END> **************************/
Expand All @@ -602,7 +607,7 @@ appldata_online_cpu(int cpu)
init_virt_timer(&per_cpu(appldata_timer, cpu));
per_cpu(appldata_timer, cpu).function = appldata_timer_function;
per_cpu(appldata_timer, cpu).data = (unsigned long)
&appldata_tasklet_struct;
&appldata_work;
atomic_inc(&appldata_expire_count);
spin_lock(&appldata_timer_lock);
__appldata_vtimer_setup(APPLDATA_MOD_TIMER);
Expand All @@ -615,7 +620,7 @@ appldata_offline_cpu(int cpu)
del_virt_timer(&per_cpu(appldata_timer, cpu));
if (atomic_dec_and_test(&appldata_expire_count)) {
atomic_set(&appldata_expire_count, num_online_cpus());
tasklet_schedule(&appldata_tasklet_struct);
queue_work(appldata_wq, &appldata_work);
}
spin_lock(&appldata_timer_lock);
__appldata_vtimer_setup(APPLDATA_MOD_TIMER);
Expand Down Expand Up @@ -648,7 +653,7 @@ static struct notifier_block __devinitdata appldata_nb = {
/*
* appldata_init()
*
* init timer and tasklet, register /proc entries
* init timer, register /proc entries
*/
static int __init appldata_init(void)
{
Expand All @@ -657,6 +662,12 @@ static int __init appldata_init(void)
P_DEBUG("sizeof(parameter_list) = %lu\n",
sizeof(struct appldata_parameter_list));

appldata_wq = create_singlethread_workqueue("appldata");
if (!appldata_wq) {
P_ERROR("Could not create work queue\n");
return -ENOMEM;
}

for_each_online_cpu(i)
appldata_online_cpu(i);

Expand All @@ -670,15 +681,14 @@ static int __init appldata_init(void)
appldata_table[1].de->owner = THIS_MODULE;
#endif

tasklet_init(&appldata_tasklet_struct, appldata_tasklet_function, 0);
P_DEBUG("Base interface initialized.\n");
return 0;
}

/*
* appldata_exit()
*
* stop timer and tasklet, unregister /proc entries
* stop timer, unregister /proc entries
*/
static void __exit appldata_exit(void)
{
Expand All @@ -690,7 +700,7 @@ static void __exit appldata_exit(void)
/*
* ops list should be empty, but just in case something went wrong...
*/
spin_lock_bh(&appldata_ops_lock);
spin_lock(&appldata_ops_lock);
list_for_each(lh, &appldata_ops_list) {
ops = list_entry(lh, struct appldata_ops, list);
rc = appldata_diag(ops->record_nr, APPLDATA_STOP_REC,
Expand All @@ -700,7 +710,7 @@ static void __exit appldata_exit(void)
"return code: %d\n", ops->name, rc);
}
}
spin_unlock_bh(&appldata_ops_lock);
spin_unlock(&appldata_ops_lock);

for_each_online_cpu(i)
appldata_offline_cpu(i);
Expand All @@ -709,7 +719,7 @@ static void __exit appldata_exit(void)

unregister_sysctl_table(appldata_sysctl_header);

tasklet_kill(&appldata_tasklet_struct);
destroy_workqueue(appldata_wq);
P_DEBUG("... module unloaded!\n");
}
/**************************** init / exit <END> ******************************/
Expand Down
2 changes: 1 addition & 1 deletion arch/s390/appldata/appldata_mem.c
View file
Expand Up @@ -68,7 +68,7 @@ struct appldata_mem_data {
u64 pgmajfault; /* page faults (major only) */
// <-- New in 2.6

} appldata_mem_data;
} __attribute__((packed)) appldata_mem_data;


static inline void appldata_debug_print(struct appldata_mem_data *mem_data)
Expand Down
2 changes: 1 addition & 1 deletion arch/s390/appldata/appldata_net_sum.c
View file
Expand Up @@ -57,7 +57,7 @@ struct appldata_net_sum_data {
u64 rx_dropped; /* no space in linux buffers */
u64 tx_dropped; /* no space available in linux */
u64 collisions; /* collisions while transmitting */
} appldata_net_sum_data;
} __attribute__((packed)) appldata_net_sum_data;


static inline void appldata_print_debug(struct appldata_net_sum_data *net_data)
Expand Down
4 changes: 2 additions & 2 deletions arch/s390/appldata/appldata_os.c
View file
Expand Up @@ -49,7 +49,7 @@ struct appldata_os_per_cpu {
u32 per_cpu_softirq; /* ... spent in softirqs */
u32 per_cpu_iowait; /* ... spent while waiting for I/O */
// <-- New in 2.6
};
} __attribute__((packed));

struct appldata_os_data {
u64 timestamp;
Expand All @@ -75,7 +75,7 @@ struct appldata_os_data {

/* per cpu data */
struct appldata_os_per_cpu os_cpu[0];
};
} __attribute__((packed));

static struct appldata_os_data *appldata_os_data;

Expand Down

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