[PATCH] firewire: core: use non-reentrant workqueue where necessary

From: Stefan Richter
Date: Sun Oct 10 2010 - 10:56:51 EST

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firewire-core manages the following types of work items:

fw_card.br_work:
- resets the bus on a card and possibly sends a PHY packet before that
- does not sleep for long or not at all
- is scheduled via fw_schedule_bus_reset() by
- firewire-ohci's pci_probe method
- firewire-ohci's set_config_rom method, called by kernelspace
protocol drivers and userspace drivers which add/remove
Configuration ROM descriptors
- userspace drivers which use the bus reset ioctl
- itself if the last reset happened less than 2 seconds ago
- should not be executed in parallel by multiple CPUs but was not
strictly protected against that

fw_card.bm_work:
- performs bus management duties
- usually does not (but may in corner cases) sleep for long
- is scheduled via fw_schedule_bm_work() by
- firewire-ohci's self-ID-complete IRQ handler tasklet
- firewire-core's fw_device.work instances whenever the root node
device was (successfully or unsuccessfully) discovered,
refreshed, or rediscovered
- itself in case of resource allocation failures or in order to
obey the 125ms bus manager arbitration interval
- must not be executed in parallel by multiple CPUs but was not
strictly protected against that

fw_device.work:
- performs node probe, update, shutdown, revival, removal; including
kernel driver probe, update, shutdown and bus reset notification to
userspace drivers
- usually sleeps moderately long, in corner cases very long
- is scheduled by
- firewire-ohci's self-ID-complete IRQ handler tasklet via the
core's fw_node_event
- firewire-ohci's pci_remove method via core's fw_destroy_nodes/
fw_node_event
- itself during retries, e.g. while a node is powering up
- must not be executed in parallel by multiple CPUs but was not
strictly protected against that

iso_resource.work:
- accesses registers at the Isochronous Resource Manager node
- usually does not (but may in corner cases) sleep for long
- is scheduled via schedule_iso_resource() by
- the owning userspace driver at addition and removal of the
resource
- firewire-core's fw_device.work instances after bus reset
- itself in case of resource allocation if necessary to obey the
1000ms reallocation period after bus reset
- must not be executed in parallel by multiple CPUs but was not
strictly protected against that

Therefore queue all of these types of work items on system_nrt_wq
instead of system_wq. The former guarantees non-reentrance across all
CPUs, the latter only on the CPU which schedules a work item.

As a bonus, other subsystems which flush system_wq won't be held up if
the firewire subsystem spends a lot of time in an extraordinarily long
fw_device.work.

Signed-off-by: Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx>
---
drivers/firewire/core-card.c | 6 +++---
drivers/firewire/core-cdev.c | 2 +-
drivers/firewire/core-device.c | 28 +++++++++++++++++-----------
3 files changed, 21 insertions(+), 15 deletions(-)

Index: b/drivers/firewire/core-card.c
===================================================================
--- a/drivers/firewire/core-card.c
+++ b/drivers/firewire/core-card.c
@@ -219,8 +219,8 @@ void fw_schedule_bus_reset(struct fw_car

/* Use an arbitrary short delay to combine multiple reset requests. */
fw_card_get(card);
- if (!schedule_delayed_work(&card->br_work,
- delayed ? DIV_ROUND_UP(HZ, 100) : 0))
+ if (!queue_delayed_work(system_nrt_wq, &card->br_work,
+ delayed ? DIV_ROUND_UP(HZ, 100) : 0))
fw_card_put(card);
}
EXPORT_SYMBOL(fw_schedule_bus_reset);
@@ -232,7 +232,7 @@ static void br_work(struct work_struct *
/* Delay for 2s after last reset per IEEE 1394 clause 8.2.1. */
if (card->reset_jiffies != 0 &&
time_is_after_jiffies(card->reset_jiffies + 2 * HZ)) {
- if (!schedule_delayed_work(&card->br_work, 2 * HZ))
+ if (!queue_delayed_work(system_nrt_wq, &card->br_work, 2 * HZ))
fw_card_put(card);
return;
}
Index: b/drivers/firewire/core-cdev.c
===================================================================
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -149,7 +149,7 @@ static void release_iso_resource(struct
static void schedule_iso_resource(struct iso_resource *r, unsigned long delay)
{
client_get(r->client);
- if (!schedule_delayed_work(&r->work, delay))
+ if (!queue_delayed_work(system_nrt_wq, &r->work, delay))
client_put(r->client);
}

Index: b/drivers/firewire/core-device.c
===================================================================
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -725,6 +725,12 @@ struct fw_device *fw_device_get_by_devt(
return device;
}

+static void fw_schedule_device_work(struct fw_device *device,
+ unsigned long delay)
+{
+ queue_delayed_work(system_nrt_wq, &device->work, delay);
+}
+
/*
* These defines control the retry behavior for reading the config
* rom. It shouldn't be necessary to tweak these; if the device
@@ -749,7 +755,7 @@ static void fw_device_shutdown(struct wo

if (time_is_after_jiffies(device->card->reset_jiffies + SHUTDOWN_DELAY)
&& !list_empty(&device->card->link)) {
- schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
+ fw_schedule_device_work(device, SHUTDOWN_DELAY);
return;
}

@@ -861,7 +867,7 @@ static int lookup_existing_device(struct
fw_notify("rediscovered device %s\n", dev_name(dev));

PREPARE_DELAYED_WORK(&old->work, fw_device_update);
- schedule_delayed_work(&old->work, 0);
+ fw_schedule_device_work(old, 0);

if (current_node == card->root_node)
fw_schedule_bm_work(card, 0);
@@ -952,7 +958,7 @@ static void fw_device_init(struct work_s
if (device->config_rom_retries < MAX_RETRIES &&
atomic_read(&device->state) == FW_DEVICE_INITIALIZING) {
device->config_rom_retries++;
- schedule_delayed_work(&device->work, RETRY_DELAY);
+ fw_schedule_device_work(device, RETRY_DELAY);
} else {
fw_notify("giving up on config rom for node id %x\n",
device->node_id);
@@ -1017,7 +1023,7 @@ static void fw_device_init(struct work_s
FW_DEVICE_INITIALIZING,
FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
- schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
+ fw_schedule_device_work(device, SHUTDOWN_DELAY);
} else {
if (device->config_rom_retries)
fw_notify("created device %s: GUID %08x%08x, S%d00, "
@@ -1096,7 +1102,7 @@ static void fw_device_refresh(struct wor
if (device->config_rom_retries < MAX_RETRIES / 2 &&
atomic_read(&device->state) == FW_DEVICE_INITIALIZING) {
device->config_rom_retries++;
- schedule_delayed_work(&device->work, RETRY_DELAY / 2);
+ fw_schedule_device_work(device, RETRY_DELAY / 2);

return;
}
@@ -1129,7 +1135,7 @@ static void fw_device_refresh(struct wor
if (device->config_rom_retries < MAX_RETRIES &&
atomic_read(&device->state) == FW_DEVICE_INITIALIZING) {
device->config_rom_retries++;
- schedule_delayed_work(&device->work, RETRY_DELAY);
+ fw_schedule_device_work(device, RETRY_DELAY);

return;
}
@@ -1156,7 +1162,7 @@ static void fw_device_refresh(struct wor
gone:
atomic_set(&device->state, FW_DEVICE_GONE);
PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
- schedule_delayed_work(&device->work, SHUTDOWN_DELAY);
+ fw_schedule_device_work(device, SHUTDOWN_DELAY);
out:
if (node_id == card->root_node->node_id)
fw_schedule_bm_work(card, 0);
@@ -1209,7 +1215,7 @@ void fw_node_event(struct fw_card *card,
* first config rom scan half a second after bus reset.
*/
INIT_DELAYED_WORK(&device->work, fw_device_init);
- schedule_delayed_work(&device->work, INITIAL_DELAY);
+ fw_schedule_device_work(device, INITIAL_DELAY);
break;

case FW_NODE_INITIATED_RESET:
@@ -1224,7 +1230,7 @@ void fw_node_event(struct fw_card *card,
FW_DEVICE_RUNNING,
FW_DEVICE_INITIALIZING) == FW_DEVICE_RUNNING) {
PREPARE_DELAYED_WORK(&device->work, fw_device_refresh);
- schedule_delayed_work(&device->work,
+ fw_schedule_device_work(device,
device->is_local ? 0 : INITIAL_DELAY);
}
break;
@@ -1239,7 +1245,7 @@ void fw_node_event(struct fw_card *card,
device->generation = card->generation;
if (atomic_read(&device->state) == FW_DEVICE_RUNNING) {
PREPARE_DELAYED_WORK(&device->work, fw_device_update);
- schedule_delayed_work(&device->work, 0);
+ fw_schedule_device_work(device, 0);
}
break;

@@ -1264,7 +1270,7 @@ void fw_node_event(struct fw_card *card,
if (atomic_xchg(&device->state,
FW_DEVICE_GONE) == FW_DEVICE_RUNNING) {
PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
- schedule_delayed_work(&device->work,
+ fw_schedule_device_work(device,
list_empty(&card->link) ? 0 : SHUTDOWN_DELAY);
}
break;

--
Stefan Richter
-=====-==-=- =-=- -=-=-
http://arcgraph.de/sr/

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Next message: Stefan Richter: "[PATCH] firewire: sbp2: parallelize login/inquiry, reconnect, andshutdown"
Previous message: Greg KH: "Re: [PATCH 2/3] Add Opticon OPN2001 write support"
Next in thread: Stefan Richter: "[PATCH] firewire: sbp2: parallelize login/inquiry, reconnect, andshutdown"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]