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Commit f26d583e authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Linus Torvalds
Browse files

[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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 595bf2aa

arch/s390/appldata/appldata_base.c

+41 −31
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
//#include <linux/kernel_stat.h>

#include <linux/notifier.h>

#include <linux/cpu.h>

#include <linux/workqueue.h>



#include "appldata.h"
@@ -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
@@ -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)

{
@@ -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) {
@@ -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 **********************************/
@@ -411,7 +415,7 @@ 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) {
@@ -419,15 +423,15 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp, 
		}

	}

	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;
@@ -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;

		}
@@ -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;
@@ -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",
@@ -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;
@@ -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> **************************/
@@ -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);
@@ -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);
@@ -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)

{
@@ -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);
@@ -670,7 +681,6 @@ 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;

}
@@ -678,7 +688,7 @@ static int __init appldata_init(void) 
/*

 * appldata_exit()

 *

 * stop timer and tasklet, unregister /proc entries

 * stop timer, unregister /proc entries

 */

static void __exit appldata_exit(void)

{
@@ -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,
@@ -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);
@@ -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> ******************************/

arch/s390/appldata/appldata_mem.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

arch/s390/appldata/appldata_net_sum.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

arch/s390/appldata/appldata_os.c

+2 −2
Original line number Diff line number Diff line
@@ -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;
@@ -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;