forked from Minki/linux
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>
This commit is contained in:
Dominik Brodowski
parent
05ce7bfe54
commit
04de081617
@ -335,7 +335,6 @@ static void pcmcia_card_remove(struct pcmcia_socket *s, struct pcmcia_device *le
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mutex_lock(&s->ops_mutex);
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list_del(&p_dev->socket_device_list);
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p_dev->_removed = 1;
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mutex_unlock(&s->ops_mutex);
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dev_dbg(&p_dev->dev, "unregistering device\n");
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@ -654,14 +653,7 @@ static int pcmcia_requery_callback(struct device *dev, void * _data)
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static void pcmcia_requery(struct pcmcia_socket *s)
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{
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int present, has_pfc;
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mutex_lock(&s->ops_mutex);
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present = s->pcmcia_state.present;
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mutex_unlock(&s->ops_mutex);
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if (!present)
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return;
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int has_pfc;
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if (s->functions == 0) {
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pcmcia_card_add(s);
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@ -1260,9 +1252,7 @@ static int ds_event(struct pcmcia_socket *skt, event_t event, int priority)
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switch (event) {
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case CS_EVENT_CARD_REMOVAL:
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mutex_lock(&s->ops_mutex);
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s->pcmcia_state.present = 0;
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mutex_unlock(&s->ops_mutex);
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atomic_set(&skt->present, 0);
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pcmcia_card_remove(skt, NULL);
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handle_event(skt, event);
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mutex_lock(&s->ops_mutex);
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@ -1271,9 +1261,9 @@ static int ds_event(struct pcmcia_socket *skt, event_t event, int priority)
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break;
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case CS_EVENT_CARD_INSERTION:
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atomic_set(&skt->present, 1);
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mutex_lock(&s->ops_mutex);
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s->pcmcia_state.has_pfc = 0;
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s->pcmcia_state.present = 1;
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destroy_cis_cache(s); /* to be on the safe side... */
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mutex_unlock(&s->ops_mutex);
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pcmcia_card_add(skt);
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@ -1313,7 +1303,13 @@ static int ds_event(struct pcmcia_socket *skt, event_t event, int priority)
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return 0;
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} /* ds_event */
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/*
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* NOTE: This is racy. There's no guarantee the card will still be
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* physically present, even if the call to this function returns
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* non-NULL. Furthermore, the device driver most likely is unbound
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* almost immediately, so the timeframe where pcmcia_dev_present
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* returns NULL is probably really really small.
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*/
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struct pcmcia_device *pcmcia_dev_present(struct pcmcia_device *_p_dev)
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{
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struct pcmcia_device *p_dev;
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@ -1323,22 +1319,9 @@ struct pcmcia_device *pcmcia_dev_present(struct pcmcia_device *_p_dev)
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if (!p_dev)
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return NULL;
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mutex_lock(&p_dev->socket->ops_mutex);
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if (!p_dev->socket->pcmcia_state.present)
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goto out;
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if (atomic_read(&p_dev->socket->present) != 0)
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ret = p_dev;
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if (p_dev->socket->pcmcia_state.dead)
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goto out;
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if (p_dev->_removed)
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goto out;
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if (p_dev->suspended)
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goto out;
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ret = p_dev;
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out:
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mutex_unlock(&p_dev->socket->ops_mutex);
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pcmcia_put_dev(p_dev);
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return ret;
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}
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@ -1388,6 +1371,8 @@ static int __devinit pcmcia_bus_add_socket(struct device *dev,
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return ret;
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}
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atomic_set(&socket->present, 0);
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return 0;
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}
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@ -1399,10 +1384,6 @@ static void pcmcia_bus_remove_socket(struct device *dev,
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if (!socket)
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return;
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mutex_lock(&socket->ops_mutex);
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socket->pcmcia_state.dead = 1;
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mutex_unlock(&socket->ops_mutex);
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pccard_register_pcmcia(socket, NULL);
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/* unregister any unbound devices */
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@ -26,6 +26,7 @@
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#ifdef __KERNEL__
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#include <linux/device.h>
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#include <pcmcia/ss.h>
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#include <asm/atomic.h>
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/*
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* PCMCIA device drivers (16-bit cards only; 32-bit cards require CardBus
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@ -94,10 +95,8 @@ struct pcmcia_device {
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config_req_t conf;
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window_handle_t win;
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/* Is the device suspended, or in the process of
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* being removed? */
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/* Is the device suspended? */
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u16 suspended:1;
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u16 _removed:1;
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/* Flags whether io, irq, win configurations were
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* requested, and whether the configuration is "locked" */
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@ -115,7 +114,7 @@ struct pcmcia_device {
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u16 has_card_id:1;
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u16 has_func_id:1;
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u16 reserved:3;
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u16 reserved:4;
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u8 func_id;
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u16 manf_id;
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@ -224,18 +224,16 @@ struct pcmcia_socket {
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/* 16-bit state: */
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struct {
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/* PCMCIA card is present in socket */
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u8 present:1;
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/* "master" ioctl is used */
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u8 busy:1;
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/* pcmcia module is being unloaded */
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u8 dead:1;
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/* the PCMCIA card consists of two pseudo devices */
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u8 has_pfc:1;
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u8 reserved:4;
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u8 reserved:6;
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} pcmcia_state;
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/* non-zero if PCMCIA card is present */
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atomic_t present;
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#ifdef CONFIG_PCMCIA_IOCTL
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struct user_info_t *user;
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