Commit 88c896ef authored by Jan Kiszka's avatar Jan Kiszka Committed by David S. Miller
Browse files

CAPI: Rework application locking 



Drop the application rw-lock in favour of RCU. This synchronizes
capi20_release against capi_ctr_handle_message which may dereference an
application from (soft-)IRQ context. Any other access to the application
list is now protected by the capi_controller_lock as well. This also
allows to safely inspect applications for /proc dumping by holding
capi_controller_lock.

At this chance, drop some useless release_in_progress checks where we
obtained the application pointer from the list (which becomes NULL on
release_in_progress).

Signed-off-by: default avatarJan Kiszka <jan.kiszka@web.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0ca3a017

drivers/isdn/capi/kcapi.c

+22 −30
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <linux/b1lli.h>

#endif

#include <linux/mutex.h>

#include <linux/rcupdate.h>



static int showcapimsgs = 0;
@@ -64,8 +65,6 @@ DEFINE_MUTEX(capi_drivers_lock); 
struct capi_ctr *capi_controller[CAPI_MAXCONTR];

DEFINE_MUTEX(capi_controller_lock);



static DEFINE_RWLOCK(application_lock);



struct capi20_appl *capi_applications[CAPI_MAXAPPL];



static int ncontrollers;
@@ -103,7 +102,7 @@ static inline struct capi20_appl *get_capi_appl_by_nr(u16 applid) 
	if (applid - 1 >= CAPI_MAXAPPL)

		return NULL;



	return capi_applications[applid - 1];

	return rcu_dereference(capi_applications[applid - 1]);

}



/* -------- util functions ------------------------------------ */
@@ -186,7 +185,7 @@ static void notify_up(u32 contr) 


		for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {

			ap = get_capi_appl_by_nr(applid);

			if (!ap || ap->release_in_progress)

			if (!ap)

				continue;

			register_appl(ctr, applid, &ap->rparam);

		}
@@ -216,7 +215,7 @@ static void ctr_down(struct capi_ctr *ctr, int new_state) 


	for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {

		ap = get_capi_appl_by_nr(applid);

		if (ap && !ap->release_in_progress)

		if (ap)

			capi_ctr_put(ctr);

	}
@@ -336,7 +335,6 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl, 
	struct capi20_appl *ap;

	int showctl = 0;

	u8 cmd, subcmd;

	unsigned long flags;

	_cdebbuf *cdb;



	if (ctr->state != CAPI_CTR_RUNNING) {
@@ -384,10 +382,10 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl, 


	}



	read_lock_irqsave(&application_lock, flags);

	rcu_read_lock();

	ap = get_capi_appl_by_nr(CAPIMSG_APPID(skb->data));

	if ((!ap) || (ap->release_in_progress)) {

		read_unlock_irqrestore(&application_lock, flags);

	if (!ap) {

		rcu_read_unlock();

		cdb = capi_message2str(skb->data);

		if (cdb) {

			printk(KERN_ERR "kcapi: handle_message: applid %d state released (%s)\n",
@@ -401,7 +399,7 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl, 
	}

	skb_queue_tail(&ap->recv_queue, skb);

	schedule_work(&ap->recv_work);

	read_unlock_irqrestore(&application_lock, flags);

	rcu_read_unlock();



	return;
@@ -656,40 +654,35 @@ u16 capi20_register(struct capi20_appl *ap) 
{

	int i;

	u16 applid;

	unsigned long flags;



	DBG("");



	if (ap->rparam.datablklen < 128)

		return CAPI_LOGBLKSIZETOSMALL;



	write_lock_irqsave(&application_lock, flags);

	ap->nrecvctlpkt = 0;

	ap->nrecvdatapkt = 0;

	ap->nsentctlpkt = 0;

	ap->nsentdatapkt = 0;

	mutex_init(&ap->recv_mtx);

	skb_queue_head_init(&ap->recv_queue);

	INIT_WORK(&ap->recv_work, recv_handler);

	ap->release_in_progress = 0;



	mutex_lock(&capi_controller_lock);



	for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {

		if (capi_applications[applid - 1] == NULL)

			break;

	}

	if (applid > CAPI_MAXAPPL) {

		write_unlock_irqrestore(&application_lock, flags);

		mutex_unlock(&capi_controller_lock);

		return CAPI_TOOMANYAPPLS;

	}



	ap->applid = applid;

	capi_applications[applid - 1] = ap;



	ap->nrecvctlpkt = 0;

	ap->nrecvdatapkt = 0;

	ap->nsentctlpkt = 0;

	ap->nsentdatapkt = 0;

	mutex_init(&ap->recv_mtx);

	skb_queue_head_init(&ap->recv_queue);

	INIT_WORK(&ap->recv_work, recv_handler);

	ap->release_in_progress = 0;



	write_unlock_irqrestore(&application_lock, flags);

	

	mutex_lock(&capi_controller_lock);



	for (i = 0; i < CAPI_MAXCONTR; i++) {

		if (!capi_controller[i] ||

		    capi_controller[i]->state != CAPI_CTR_RUNNING)
@@ -721,16 +714,15 @@ EXPORT_SYMBOL(capi20_register); 
u16 capi20_release(struct capi20_appl *ap)

{

	int i;

	unsigned long flags;



	DBG("applid %#x", ap->applid);



	write_lock_irqsave(&application_lock, flags);

	mutex_lock(&capi_controller_lock);



	ap->release_in_progress = 1;

	capi_applications[ap->applid - 1] = NULL;

	write_unlock_irqrestore(&application_lock, flags);



	mutex_lock(&capi_controller_lock);

	synchronize_rcu();



	for (i = 0; i < CAPI_MAXCONTR; i++) {

		if (!capi_controller[i] ||

drivers/isdn/capi/kcapi_proc.c

+7 −4
Original line number Diff line number Diff line
@@ -139,9 +139,11 @@ static const struct file_operations proc_contrstats_ops = { 
//      applid nrecvctlpkt nrecvdatapkt nsentctlpkt nsentdatapkt

// ---------------------------------------------------------------------------



static void *

applications_start(struct seq_file *seq, loff_t *pos)

static void *applications_start(struct seq_file *seq, loff_t *pos)

	__acquires(capi_controller_lock)

{

	mutex_lock(&capi_controller_lock);



	if (*pos < CAPI_MAXAPPL)

		return &capi_applications[*pos];
@@ -158,9 +160,10 @@ applications_next(struct seq_file *seq, void *v, loff_t *pos) 
	return NULL;

}



static void

applications_stop(struct seq_file *seq, void *v)

static void applications_stop(struct seq_file *seq, void *v)

	__releases(capi_controller_lock)

{

	mutex_unlock(&capi_controller_lock);

}



static int

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