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: Stefan 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: Jarod Wilson <jwilson@redhat.com> Signed-off-by: Kristian Høgsberg <krh@redhat.com>
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@ -207,6 +207,7 @@ fill_bus_reset_event(struct fw_cdev_event_bus_reset *event,
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event->closure = client->bus_reset_closure;
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event->type = FW_CDEV_EVENT_BUS_RESET;
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event->generation = client->device->generation;
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smp_rmb(); /* node_id must not be older than generation */
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event->node_id = client->device->node_id;
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event->local_node_id = card->local_node->node_id;
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event->bm_node_id = 0; /* FIXME: We don't track the BM. */
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@ -27,6 +27,7 @@
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#include <linux/idr.h>
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#include <linux/rwsem.h>
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#include <asm/semaphore.h>
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#include <asm/system.h>
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#include <linux/ctype.h>
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#include "fw-transaction.h"
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#include "fw-topology.h"
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@ -182,9 +183,14 @@ static void fw_device_release(struct device *dev)
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int fw_device_enable_phys_dma(struct fw_device *device)
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{
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int generation = device->generation;
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/* device->node_id, accessed below, must not be older than generation */
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smp_rmb();
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return device->card->driver->enable_phys_dma(device->card,
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device->node_id,
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device->generation);
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generation);
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}
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EXPORT_SYMBOL(fw_device_enable_phys_dma);
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@ -389,12 +395,16 @@ static int read_rom(struct fw_device *device, int index, u32 * data)
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struct read_quadlet_callback_data callback_data;
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struct fw_transaction t;
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u64 offset;
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int generation = device->generation;
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/* device->node_id, accessed below, must not be older than generation */
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smp_rmb();
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init_completion(&callback_data.done);
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offset = 0xfffff0000400ULL + index * 4;
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fw_send_request(device->card, &t, TCODE_READ_QUADLET_REQUEST,
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device->node_id, device->generation, device->max_speed,
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device->node_id, generation, device->max_speed,
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offset, NULL, 4, complete_transaction, &callback_data);
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wait_for_completion(&callback_data.done);
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@ -801,6 +811,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
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device = node->data;
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device->node_id = node->node_id;
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smp_wmb(); /* update node_id before generation */
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device->generation = card->generation;
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if (atomic_read(&device->state) == FW_DEVICE_RUNNING) {
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PREPARE_DELAYED_WORK(&device->work, fw_device_update);
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@ -35,6 +35,18 @@ struct fw_attribute_group {
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struct attribute *attrs[11];
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};
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/*
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* Note, fw_device.generation always has to be read before fw_device.node_id.
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* Use SMP memory barriers to ensure this. Otherwise requests will be sent
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* to an outdated node_id if the generation was updated in the meantime due
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* to a bus reset.
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*
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* Likewise, fw-core will take care to update .node_id before .generation so
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* that whenever fw_device.generation is current WRT the actual bus generation,
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* fw_device.node_id is guaranteed to be current too.
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*
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* The same applies to fw_device.card->node_id vs. fw_device.generation.
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*/
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struct fw_device {
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atomic_t state;
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struct fw_node *node;
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@ -40,6 +40,7 @@
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#include <linux/stringify.h>
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#include <linux/timer.h>
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#include <linux/workqueue.h>
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#include <asm/system.h>
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#include <scsi/scsi.h>
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#include <scsi/scsi_cmnd.h>
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@ -662,6 +663,7 @@ static void sbp2_login(struct work_struct *work)
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int generation, node_id, local_node_id;
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generation = device->generation;
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smp_rmb(); /* node_id must not be older than generation */
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node_id = device->node_id;
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local_node_id = device->card->node_id;
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@ -912,6 +914,7 @@ static void sbp2_reconnect(struct work_struct *work)
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int generation, node_id, local_node_id;
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generation = device->generation;
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smp_rmb(); /* node_id must not be older than generation */
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node_id = device->node_id;
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local_node_id = device->card->node_id;
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@ -21,6 +21,7 @@
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#include <linux/module.h>
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#include <linux/wait.h>
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#include <linux/errno.h>
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#include <asm/system.h>
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#include "fw-transaction.h"
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#include "fw-topology.h"
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@ -518,6 +519,11 @@ fw_core_handle_bus_reset(struct fw_card *card,
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card->bm_retries = 0;
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card->node_id = node_id;
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/*
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* Update node_id before generation to prevent anybody from using
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* a stale node_id together with a current generation.
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*/
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smp_wmb();
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card->generation = generation;
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card->reset_jiffies = jiffies;
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schedule_delayed_work(&card->work, 0);
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