RE: [PATCH 3/5] rapidio: run discovery as an asynchronous process
On Wed, October 03, 2012 6:30 PM
Andrew Morton a...@linux-foundation.org wrote:
On Wed, 3 Oct 2012 15:18:41 -0400
Alexandre Bounine alexandre.boun...@idt.com wrote:
...
+static void __devinit disc_work_handler(struct work_struct *_work)
+{
+ struct rio_disc_work *work = container_of(_work,
+ struct rio_disc_work, work);
There's a nice simple way to avoid such ugliness:
--- a/drivers/rapidio/rio.c~rapidio-run-discovery-as-an-asynchronous-
process-fix
+++ a/drivers/rapidio/rio.c
@@ -1269,9 +1269,9 @@ struct rio_disc_work {
static void __devinit disc_work_handler(struct work_struct *_work)
{
- struct rio_disc_work *work = container_of(_work,
- struct rio_disc_work, work);
+ struct rio_disc_work *work;
+ work = container_of(_work, struct rio_disc_work, work);
pr_debug(RIO: discovery work for mport %d %s\n,
work-mport-id, work-mport-name);
rio_disc_mport(work-mport);
_
Thank you for the fix. Will avoid that ugliness in the future.
+ pr_debug(RIO: discovery work for mport %d %s\n,
+work-mport-id, work-mport-name);
+ rio_disc_mport(work-mport);
+
+ kfree(work);
+}
+
int __devinit rio_init_mports(void)
{
struct rio_mport *port;
+ struct rio_disc_work *work;
+ int no_disc = 0;
list_for_each_entry(port, rio_mports, node) {
if (port-host_deviceid = 0)
rio_enum_mport(port);
- else
- rio_disc_mport(port);
+ else if (!no_disc) {
+ if (!rio_wq) {
+ rio_wq = alloc_workqueue(riodisc, 0, 0);
+ if (!rio_wq) {
+ pr_err(RIO: unable allocate rio_wq\n);
+ no_disc = 1;
+ continue;
+ }
+ }
+
+ work = kzalloc(sizeof *work, GFP_KERNEL);
+ if (!work) {
+ pr_err(RIO: no memory for work struct\n);
+ no_disc = 1;
+ continue;
+ }
+
+ work-mport = port;
+ INIT_WORK(work-work, disc_work_handler);
+ queue_work(rio_wq, work-work);
+ }
+ }
I'm having a lot of trouble with `no_disc'. afacit what it does is to
cease running async discovery for any remaining devices if the
workqueue
allocation failed (vaguely reasonable) or if the allocation of a single
work item failed (incomprehensible).
But if we don't run discovery, the subsystem is permanently busted for
at least some devices, isn't it?
This is correct. We are considering ways to restart discovery
process later but it is not applicable now.
And this code is basically untestable unless the programmer does
deliberate fault injection, which makes it pretty much unmaintainable.
So... if I haven't totally misunderstood, I suggest a rethink is in
order?
I will review and simplify. Probably, just try to allocate all required
resources ahead of port list scan. Simple and safe.
+ if (rio_wq) {
+ pr_debug(RIO: flush discovery workqueue\n);
+ flush_workqueue(rio_wq);
+ pr_debug(RIO: flush discovery workqueue finished\n);
+ destroy_workqueue(rio_wq);
}
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Re: [PATCH 3/5] rapidio: run discovery as an asynchronous process
On Wed, 3 Oct 2012 15:18:41 -0400
Alexandre Bounine alexandre.boun...@idt.com wrote:
Modify mport initialization routine to run the RapidIO discovery process
asynchronously. This allows to have an arbitrary order of enumerating and
discovering ports in systems with multiple RapidIO controllers without
creating a deadlock situation if enumerator port is registered after a
discovering one.
Making netID matching to mportID ensures consistent net ID assignment in
multiport RapidIO systems with asynchronous discovery process (global counter
implementation is affected by race between threads).
...
+static void __devinit disc_work_handler(struct work_struct *_work)
+{
+ struct rio_disc_work *work = container_of(_work,
+ struct rio_disc_work, work);
There's a nice simple way to avoid such ugliness:
--- a/drivers/rapidio/rio.c~rapidio-run-discovery-as-an-asynchronous-process-fix
+++ a/drivers/rapidio/rio.c
@@ -1269,9 +1269,9 @@ struct rio_disc_work {
static void __devinit disc_work_handler(struct work_struct *_work)
{
- struct rio_disc_work *work = container_of(_work,
- struct rio_disc_work, work);
+ struct rio_disc_work *work;
+ work = container_of(_work, struct rio_disc_work, work);
pr_debug(RIO: discovery work for mport %d %s\n,
work-mport-id, work-mport-name);
rio_disc_mport(work-mport);
_
+ pr_debug(RIO: discovery work for mport %d %s\n,
+ work-mport-id, work-mport-name);
+ rio_disc_mport(work-mport);
+
+ kfree(work);
+}
+
int __devinit rio_init_mports(void)
{
struct rio_mport *port;
+ struct rio_disc_work *work;
+ int no_disc = 0;
list_for_each_entry(port, rio_mports, node) {
if (port-host_deviceid = 0)
rio_enum_mport(port);
- else
- rio_disc_mport(port);
+ else if (!no_disc) {
+ if (!rio_wq) {
+ rio_wq = alloc_workqueue(riodisc, 0, 0);
+ if (!rio_wq) {
+ pr_err(RIO: unable allocate rio_wq\n);
+ no_disc = 1;
+ continue;
+ }
+ }
+
+ work = kzalloc(sizeof *work, GFP_KERNEL);
+ if (!work) {
+ pr_err(RIO: no memory for work struct\n);
+ no_disc = 1;
+ continue;
+ }
+
+ work-mport = port;
+ INIT_WORK(work-work, disc_work_handler);
+ queue_work(rio_wq, work-work);
+ }
+ }
I'm having a lot of trouble with `no_disc'. afacit what it does is to
cease running async discovery for any remaining devices if the workqueue
allocation failed (vaguely reasonable) or if the allocation of a single
work item failed (incomprehensible).
But if we don't run discovery, the subsystem is permanently busted for
at least some devices, isn't it?
And this code is basically untestable unless the programmer does
deliberate fault injection, which makes it pretty much unmaintainable.
So... if I haven't totally misunderstood, I suggest a rethink is in
order?
+ if (rio_wq) {
+ pr_debug(RIO: flush discovery workqueue\n);
+ flush_workqueue(rio_wq);
+ pr_debug(RIO: flush discovery workqueue finished\n);
+ destroy_workqueue(rio_wq);
}
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