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Date: Sat, 17 Jan 2009 22:46:28 +0100 (CET)
From: Stefan Richter <stefanr@...6.in-berlin.de>
To: linux1394-devel@...ts.sourceforge.net
cc: linux-kernel@...r.kernel.org
Subject: [PATCH 1/4] firewire: keep highlevel drivers attached during brief
connection loss
Date:
From: Stefan Richter <stefanr@...6.in-berlin.de>
Subject: firewire: keep highlevel drivers attached during brief connection loss
There are situations when nodes vanish from the bus and come back in
quickly thereafter:
- When certain bus-powered hubs are plugged in,
- when certain devices are plugged into 6-port hubs,
- when certain disk enclosures are switched from self-power to bus
power or vice versa and break the daisy chain during the transition,
- when the user plugs a cable out and quickly plugs it back in, e.g.
to reorder a daisy chain (works on Mac OS X if done quickly enough),
- when certain hubs temporarily malfunction during high bus traffic.
Until now, firewire-core reported affected nodes as lost to the
highlevel drivers (firewire-sbp2 and userspace drivers). We now delay
the destruction of device representations until after at least two
seconds after the last bus reset. If a "new" device is detected in this
period whose bus information block and root directory header match that
of a device which is pending for deletion, we resurrect that device and
send update calls to highlevel drivers.
Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
drivers/firewire/fw-device.c | 121 ++++++++++++++++++++++++++++-------
drivers/firewire/fw-device.h | 1
2 files changed, 100 insertions(+), 22 deletions(-)
Index: linux/drivers/firewire/fw-device.c
===================================================================
--- linux.orig/drivers/firewire/fw-device.c
+++ linux/drivers/firewire/fw-device.c
@@ -25,6 +25,7 @@
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/idr.h>
+#include <linux/jiffies.h>
#include <linux/string.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
@@ -632,12 +633,38 @@ struct fw_device *fw_device_get_by_devt(
return device;
}
+/*
+ * These defines control the retry behavior for reading the config
+ * rom. It shouldn't be necessary to tweak these; if the device
+ * doesn't respond to a config rom read within 10 seconds, it's not
+ * going to respond at all. As for the initial delay, a lot of
+ * devices will be able to respond within half a second after bus
+ * reset. On the other hand, it's not really worth being more
+ * aggressive than that, since it scales pretty well; if 10 devices
+ * are plugged in, they're all getting read within one second.
+ */
+
+#define MAX_RETRIES 10
+#define RETRY_DELAY (3 * HZ)
+#define INITIAL_DELAY (HZ / 2)
+#define SHUTDOWN_DELAY (2 * HZ)
+
static void fw_device_shutdown(struct work_struct *work)
{
struct fw_device *device =
container_of(work, struct fw_device, work.work);
int minor = MINOR(device->device.devt);
+ if (time_is_after_jiffies(device->card->reset_jiffies + SHUTDOWN_DELAY)) {
+ schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
+ return;
+ }
+
+ if (atomic_cmpxchg(&device->state,
+ FW_DEVICE_GONE,
+ FW_DEVICE_SHUTDOWN) != FW_DEVICE_GONE)
+ return;
+
fw_device_cdev_remove(device);
device_for_each_child(&device->device, NULL, shutdown_unit);
device_unregister(&device->device);
@@ -645,6 +672,7 @@ static void fw_device_shutdown(struct wo
down_write(&fw_device_rwsem);
idr_remove(&fw_device_idr, minor);
up_write(&fw_device_rwsem);
+
fw_device_put(device);
}
@@ -652,25 +680,63 @@ static struct device_type fw_device_type
.release = fw_device_release,
};
+static void fw_device_update(struct work_struct *work);
+
/*
- * These defines control the retry behavior for reading the config
- * rom. It shouldn't be necessary to tweak these; if the device
- * doesn't respond to a config rom read within 10 seconds, it's not
- * going to respond at all. As for the initial delay, a lot of
- * devices will be able to respond within half a second after bus
- * reset. On the other hand, it's not really worth being more
- * aggressive than that, since it scales pretty well; if 10 devices
- * are plugged in, they're all getting read within one second.
+ * If a device was pending for deletion because its node went away but its
+ * bus info block and root directory header matches that of a newly discovered
+ * device, revive the existing fw_device.
+ * The newly allocated fw_device becomes obsolete instead.
*/
+static int lookup_existing_device(struct device *dev, void *data)
+{
+ struct fw_device *old = fw_device(dev);
+ struct fw_device *new = data;
+ struct fw_card *card = new->card;
+ int match = 0;
+
+ down_read(&fw_device_rwsem); /* serialize config_rom access */
+ spin_lock_irq(&card->lock); /* serialize node access */
+
+ if (memcmp(old->config_rom, new->config_rom, 6 * 4) == 0 &&
+ atomic_cmpxchg(&old->state,
+ FW_DEVICE_GONE,
+ FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
+ struct fw_node *current_node = new->node;
+ struct fw_node *obsolete_node = old->node;
+
+ new->node = obsolete_node;
+ new->node->data = new;
+ old->node = current_node;
+ old->node->data = old;
-#define MAX_RETRIES 10
-#define RETRY_DELAY (3 * HZ)
-#define INITIAL_DELAY (HZ / 2)
+ old->max_speed = new->max_speed;
+ old->node_id = current_node->node_id;
+ smp_wmb(); /* update node_id before generation */
+ old->generation = card->generation;
+ old->config_rom_retries = 0;
+ fw_notify("rediscovered device %s\n", dev_name(dev));
+
+ PREPARE_DELAYED_WORK(&old->work, fw_device_update);
+ schedule_delayed_work(&old->work, 0);
+
+ if (current_node == card->root_node)
+ fw_schedule_bm_work(card, 0);
+
+ match = 1;
+ }
+
+ spin_unlock_irq(&card->lock);
+ up_read(&fw_device_rwsem);
+
+ return match;
+}
static void fw_device_init(struct work_struct *work)
{
struct fw_device *device =
container_of(work, struct fw_device, work.work);
+ struct device *revived_dev;
int minor, err;
/*
@@ -694,6 +760,15 @@ static void fw_device_init(struct work_s
return;
}
+ revived_dev = device_find_child(device->card->device,
+ device, lookup_existing_device);
+ if (revived_dev) {
+ put_device(revived_dev);
+ fw_device_release(&device->device);
+
+ return;
+ }
+
device_initialize(&device->device);
fw_device_get(device);
@@ -732,9 +807,10 @@ static void fw_device_init(struct work_s
* fw_node_event().
*/
if (atomic_cmpxchg(&device->state,
- FW_DEVICE_INITIALIZING,
- FW_DEVICE_RUNNING) == FW_DEVICE_SHUTDOWN) {
- fw_device_shutdown(work);
+ FW_DEVICE_INITIALIZING,
+ FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
+ PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
+ schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
} else {
if (device->config_rom_retries)
fw_notify("created device %s: GUID %08x%08x, S%d00, "
@@ -845,8 +921,8 @@ static void fw_device_refresh(struct wor
case REREAD_BIB_UNCHANGED:
if (atomic_cmpxchg(&device->state,
- FW_DEVICE_INITIALIZING,
- FW_DEVICE_RUNNING) == FW_DEVICE_SHUTDOWN)
+ FW_DEVICE_INITIALIZING,
+ FW_DEVICE_RUNNING) == FW_DEVICE_GONE)
goto gone;
fw_device_update(work);
@@ -877,8 +953,8 @@ static void fw_device_refresh(struct wor
create_units(device);
if (atomic_cmpxchg(&device->state,
- FW_DEVICE_INITIALIZING,
- FW_DEVICE_RUNNING) == FW_DEVICE_SHUTDOWN)
+ FW_DEVICE_INITIALIZING,
+ FW_DEVICE_RUNNING) == FW_DEVICE_GONE)
goto gone;
fw_notify("refreshed device %s\n", dev_name(&device->device));
@@ -888,8 +964,9 @@ static void fw_device_refresh(struct wor
give_up:
fw_notify("giving up on refresh of device %s\n", dev_name(&device->device));
gone:
- atomic_set(&device->state, FW_DEVICE_SHUTDOWN);
- fw_device_shutdown(work);
+ atomic_set(&device->state, FW_DEVICE_GONE);
+ PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
+ schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
out:
if (node_id == card->root_node->node_id)
fw_schedule_bm_work(card, 0);
@@ -994,9 +1071,9 @@ void fw_node_event(struct fw_card *card,
*/
device = node->data;
if (atomic_xchg(&device->state,
- FW_DEVICE_SHUTDOWN) == FW_DEVICE_RUNNING) {
+ FW_DEVICE_GONE) == FW_DEVICE_RUNNING) {
PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
- schedule_delayed_work(&device->work, 0);
+ schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
}
break;
}
Index: linux/drivers/firewire/fw-device.h
===================================================================
--- linux.orig/drivers/firewire/fw-device.h
+++ linux/drivers/firewire/fw-device.h
@@ -29,6 +29,7 @@
enum fw_device_state {
FW_DEVICE_INITIALIZING,
FW_DEVICE_RUNNING,
+ FW_DEVICE_GONE,
FW_DEVICE_SHUTDOWN,
};
--
Stefan Richter
-=====-==--= ---= =---=
http://arcgraph.de/sr/
--
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