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Commit b5d2a5e0 authored by Stefan Richter's avatar Stefan Richter
Browse files

firewire: enforce access order between generation and node ID, fix "giving up on config rom" 

fw_device.node_id and fw_device.generation are accessed without mutexes.
We have to ensure that all readers will get to see node_id updates
before generation updates.

Fixes an inability to recognize devices after "giving up on config rom",
https://bugzilla.redhat.com/show_bug.cgi?id=429950



Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>

Reviewed by Nick Piggin <nickpiggin@yahoo.com.au>.

Verified to fix 'giving up on config rom' issues on multiple system and
drive combinations that were previously affected.

Signed-off-by: default avatarJarod Wilson <jwilson@redhat.com>
Signed-off-by: default avatarKristian Høgsberg <krh@redhat.com>
parent cf5a56ac

drivers/firewire/fw-cdev.c

+1 −0
Original line number Diff line number Diff line
@@ -207,6 +207,7 @@ fill_bus_reset_event(struct fw_cdev_event_bus_reset *event, 
	event->closure	     = client->bus_reset_closure;

	event->type          = FW_CDEV_EVENT_BUS_RESET;

	event->generation    = client->device->generation;

	smp_rmb();           /* node_id must not be older than generation */

	event->node_id       = client->device->node_id;

	event->local_node_id = card->local_node->node_id;

	event->bm_node_id    = 0; /* FIXME: We don't track the BM. */

drivers/firewire/fw-device.c

+13 −2
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <linux/idr.h>

#include <linux/rwsem.h>

#include <asm/semaphore.h>

#include <asm/system.h>

#include <linux/ctype.h>

#include "fw-transaction.h"

#include "fw-topology.h"
@@ -182,9 +183,14 @@ static void fw_device_release(struct device *dev) 


int fw_device_enable_phys_dma(struct fw_device *device)

{

	int generation = device->generation;



	/* device->node_id, accessed below, must not be older than generation */

	smp_rmb();



	return device->card->driver->enable_phys_dma(device->card,

						     device->node_id,

						     device->generation);

						     generation);

}

EXPORT_SYMBOL(fw_device_enable_phys_dma);
@@ -389,12 +395,16 @@ static int read_rom(struct fw_device *device, int index, u32 * data) 
	struct read_quadlet_callback_data callback_data;

	struct fw_transaction t;

	u64 offset;

	int generation = device->generation;



	/* device->node_id, accessed below, must not be older than generation */

	smp_rmb();



	init_completion(&callback_data.done);



	offset = 0xfffff0000400ULL + index * 4;

	fw_send_request(device->card, &t, TCODE_READ_QUADLET_REQUEST,

			device->node_id, device->generation, device->max_speed,

			device->node_id, generation, device->max_speed,

			offset, NULL, 4, complete_transaction, &callback_data);



	wait_for_completion(&callback_data.done);
@@ -801,6 +811,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event) 


		device = node->data;

		device->node_id = node->node_id;

		smp_wmb();  /* update node_id before generation */

		device->generation = card->generation;

		if (atomic_read(&device->state) == FW_DEVICE_RUNNING) {

			PREPARE_DELAYED_WORK(&device->work, fw_device_update);

drivers/firewire/fw-device.h

+12 −0
Original line number Diff line number Diff line
@@ -35,6 +35,18 @@ struct fw_attribute_group { 
	struct attribute *attrs[11];

};



/*

 * Note, fw_device.generation always has to be read before fw_device.node_id.

 * Use SMP memory barriers to ensure this.  Otherwise requests will be sent

 * to an outdated node_id if the generation was updated in the meantime due

 * to a bus reset.

 *

 * Likewise, fw-core will take care to update .node_id before .generation so

 * that whenever fw_device.generation is current WRT the actual bus generation,

 * fw_device.node_id is guaranteed to be current too.

 *

 * The same applies to fw_device.card->node_id vs. fw_device.generation.

 */

struct fw_device {

	atomic_t state;

	struct fw_node *node;

drivers/firewire/fw-sbp2.c

+3 −0
Original line number Diff line number Diff line
@@ -40,6 +40,7 @@ 
#include <linux/stringify.h>

#include <linux/timer.h>

#include <linux/workqueue.h>

#include <asm/system.h>



#include <scsi/scsi.h>

#include <scsi/scsi_cmnd.h>
@@ -662,6 +663,7 @@ static void sbp2_login(struct work_struct *work) 
	int generation, node_id, local_node_id;



	generation    = device->generation;

	smp_rmb();    /* node_id must not be older than generation */

	node_id       = device->node_id;

	local_node_id = device->card->node_id;
@@ -912,6 +914,7 @@ static void sbp2_reconnect(struct work_struct *work) 
	int generation, node_id, local_node_id;



	generation    = device->generation;

	smp_rmb();    /* node_id must not be older than generation */

	node_id       = device->node_id;

	local_node_id = device->card->node_id;

drivers/firewire/fw-topology.c

+6 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/module.h>

#include <linux/wait.h>

#include <linux/errno.h>

#include <asm/system.h>

#include "fw-transaction.h"

#include "fw-topology.h"
@@ -518,6 +519,11 @@ fw_core_handle_bus_reset(struct fw_card *card, 
		card->bm_retries = 0;



	card->node_id = node_id;

	/*

	 * Update node_id before generation to prevent anybody from using

	 * a stale node_id together with a current generation.

	 */

	smp_wmb();

	card->generation = generation;

	card->reset_jiffies = jiffies;

	schedule_delayed_work(&card->work, 0);