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pcmcia: pcmcia_dev_present bugfix

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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>
This commit is contained in:
Dominik Brodowski 2010-04-20 14:49:01 +02:00
parent 05ce7bfe54
commit 04de081617
3 changed files with 20 additions and 42 deletions
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47
drivers/pcmcia/ds.c
View File

@ -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 */

7
include/pcmcia/ds.h
View File

@ -26,6 +26,7 @@
#ifdef __KERNEL__
#include <linux/device.h>
#include <pcmcia/ss.h>
#include <asm/atomic.h>
/*
* PCMCIA device drivers (16-bit cards only; 32-bit cards require CardBus
@ -94,10 +95,8 @@ struct pcmcia_device {
config_req_t conf;
window_handle_t win;
/* Is the device suspended, or in the process of
* being removed? */
/* Is the device suspended? */
u16 suspended:1;
u16 _removed:1;
/* Flags whether io, irq, win configurations were
* requested, and whether the configuration is "locked" */
@ -115,7 +114,7 @@ struct pcmcia_device {
u16 has_card_id:1;
u16 has_func_id:1;
u16 reserved:3;
u16 reserved:4;
u8 func_id;
u16 manf_id;

8
include/pcmcia/ss.h
View File

@ -224,18 +224,16 @@ struct pcmcia_socket {
/* 16-bit state: */
struct {
/* PCMCIA card is present in socket */
u8 present:1;
/* "master" ioctl is used */
u8 busy:1;
/* pcmcia module is being unloaded */
u8 dead:1;
/* the PCMCIA card consists of two pseudo devices */
u8 has_pfc:1;
u8 reserved:4;
u8 reserved:6;
} pcmcia_state;
/* non-zero if PCMCIA card is present */
atomic_t present;
#ifdef CONFIG_PCMCIA_IOCTL
struct user_info_t *user;