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CAPI: Rework application locking

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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: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jan Kiszka 2010-02-08 10:12:15 +00:00 committed by David S. Miller
parent 0ca3a017a7
commit 88c896ef87
2 changed files with 30 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
drivers/isdn/capi/kcapi.c
View File

@ -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;
@ -656,27 +654,12 @@ 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);
for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {
if (capi_applications[applid - 1] == NULL)
break;
}
if (applid > CAPI_MAXAPPL) {
write_unlock_irqrestore(&application_lock, flags);
return CAPI_TOOMANYAPPLS;
}
ap->applid = applid;
capi_applications[applid - 1] = ap;
ap->nrecvctlpkt = 0;
ap->nrecvdatapkt = 0;
ap->nsentctlpkt = 0;
@ -686,10 +669,20 @@ u16 capi20_register(struct capi20_appl *ap)
INIT_WORK(&ap->recv_work, recv_handler);
ap->release_in_progress = 0;
write_unlock_irqrestore(&application_lock, flags);
mutex_lock(&capi_controller_lock);
for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {
if (capi_applications[applid - 1] == NULL)
break;
}
if (applid > CAPI_MAXAPPL) {
mutex_unlock(&capi_controller_lock);
return CAPI_TOOMANYAPPLS;
}
ap->applid = applid;
capi_applications[applid - 1] = ap;
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] ||

11
drivers/isdn/capi/kcapi_proc.c
View File

@ -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