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Commit 04de0816 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

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: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 05ce7bfe

drivers/pcmcia/ds.c

+14 −33
Original line number Diff line number Diff line
@@ -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 (p_dev->socket->pcmcia_state.dead)

		goto out;



	if (p_dev->_removed)

		goto out;



	if (p_dev->suspended)

		goto out;



	if (atomic_read(&p_dev->socket->present) != 0)

		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 */

include/pcmcia/ds.h

+3 −4
Original line number Diff line number Diff line
@@ -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;

include/pcmcia/ss.h

+3 −5
Original line number Diff line number Diff line
@@ -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;