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authorDominik Brodowski <linux@dominikbrodowski.net>2010-04-20 14:49:01 +0200
committerDominik Brodowski <linux@dominikbrodowski.net>2010-04-21 08:09:17 +0200
commit04de0816173c86948b75da93a6344a0a02bbec4d (patch)
treeed4b274c1ce5da03a9c37f5858a331529e5b150f /drivers/pcmcia
parent05ce7bfe547c9fa967d9cab6c37867a9cb6fb3fa (diff)
downloadlinux-2.6.34-ux500-04de0816173c86948b75da93a6344a0a02bbec4d.tar.gz
pcmcia: pcmcia_dev_present bugfix
pcmcia_dev_present is in and by itself buggy. Add a note specifying why it is broken, and replace the broken locking -- taking a mutex is a bad idea in IRQ context, from which this function is rarely called -- by an atomic_t. Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Diffstat (limited to 'drivers/pcmcia')
-rw-r--r--drivers/pcmcia/ds.c47
1 files changed, 14 insertions, 33 deletions
diff --git a/drivers/pcmcia/ds.c b/drivers/pcmcia/ds.c
index 4014cf8e4a2..92a5af8aa0b 100644
--- a/drivers/pcmcia/ds.c
+++ b/drivers/pcmcia/ds.c
@@ -335,7 +335,6 @@ static void pcmcia_card_remove(struct pcmcia_socket *s, struct pcmcia_device *le
mutex_lock(&s->ops_mutex);
list_del(&p_dev->socket_device_list);
- p_dev->_removed = 1;
mutex_unlock(&s->ops_mutex);
dev_dbg(&p_dev->dev, "unregistering device\n");
@@ -654,14 +653,7 @@ static int pcmcia_requery_callback(struct device *dev, void * _data)
static void pcmcia_requery(struct pcmcia_socket *s)
{
- int present, has_pfc;
-
- mutex_lock(&s->ops_mutex);
- present = s->pcmcia_state.present;
- mutex_unlock(&s->ops_mutex);
-
- if (!present)
- return;
+ int has_pfc;
if (s->functions == 0) {
pcmcia_card_add(s);
@@ -1260,9 +1252,7 @@ static int ds_event(struct pcmcia_socket *skt, event_t event, int priority)
switch (event) {
case CS_EVENT_CARD_REMOVAL:
- mutex_lock(&s->ops_mutex);
- s->pcmcia_state.present = 0;
- mutex_unlock(&s->ops_mutex);
+ atomic_set(&skt->present, 0);
pcmcia_card_remove(skt, NULL);
handle_event(skt, event);
mutex_lock(&s->ops_mutex);
@@ -1271,9 +1261,9 @@ static int ds_event(struct pcmcia_socket *skt, event_t event, int priority)
break;
case CS_EVENT_CARD_INSERTION:
+ atomic_set(&skt->present, 1);
mutex_lock(&s->ops_mutex);
s->pcmcia_state.has_pfc = 0;
- s->pcmcia_state.present = 1;
destroy_cis_cache(s); /* to be on the safe side... */
mutex_unlock(&s->ops_mutex);
pcmcia_card_add(skt);
@@ -1313,7 +1303,13 @@ static int ds_event(struct pcmcia_socket *skt, event_t event, int priority)
return 0;
} /* ds_event */
-
+/*
+ * NOTE: This is racy. There's no guarantee the card will still be
+ * physically present, even if the call to this function returns
+ * non-NULL. Furthermore, the device driver most likely is unbound
+ * almost immediately, so the timeframe where pcmcia_dev_present
+ * returns NULL is probably really really small.
+ */
struct pcmcia_device *pcmcia_dev_present(struct pcmcia_device *_p_dev)
{
struct pcmcia_device *p_dev;
@@ -1323,22 +1319,9 @@ struct pcmcia_device *pcmcia_dev_present(struct pcmcia_device *_p_dev)
if (!p_dev)
return NULL;
- mutex_lock(&p_dev->socket->ops_mutex);
- if (!p_dev->socket->pcmcia_state.present)
- goto out;
+ if (atomic_read(&p_dev->socket->present) != 0)
+ ret = p_dev;
- if (p_dev->socket->pcmcia_state.dead)
- goto out;
-
- if (p_dev->_removed)
- goto out;
-
- if (p_dev->suspended)
- goto out;
-
- ret = p_dev;
- out:
- mutex_unlock(&p_dev->socket->ops_mutex);
pcmcia_put_dev(p_dev);
return ret;
}
@@ -1388,6 +1371,8 @@ static int __devinit pcmcia_bus_add_socket(struct device *dev,
return ret;
}
+ atomic_set(&socket->present, 0);
+
return 0;
}
@@ -1399,10 +1384,6 @@ static void pcmcia_bus_remove_socket(struct device *dev,
if (!socket)
return;
- mutex_lock(&socket->ops_mutex);
- socket->pcmcia_state.dead = 1;
- mutex_unlock(&socket->ops_mutex);
-
pccard_register_pcmcia(socket, NULL);
/* unregister any unbound devices */