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: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/isdn/capi/kcapi.c b/drivers/isdn/capi/kcapi.c
index a99f7e3..0b4c8a7 100644
--- a/drivers/isdn/capi/kcapi.c
+++ b/drivers/isdn/capi/kcapi.c
@@ -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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
}
- 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 @@
}
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 @@
{
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 @@
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 @@
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] ||