On Thu, 13 Oct 2011, Henrik Rydberg wrote:
> > It's always a bug. However, the patch I sent to Matthew should fix the
> > immediate problem.
> >
> > In fact, the original autosuspend design intended to allow drivers to
> > do this -- keep devices awake by failing suspend requests even though
> > the usage count is 0. Under some conditions, that's the approach with
> > the least overhead. But the code to handle this got lost by mistake,
> > so now it needs to be added back.
>
> I tried the patch out, unfortunately it did not work. The second
> suspend request returns with a -EINPROGRESS, here:
>
> if (dev->power.runtime_status == RPM_SUSPENDING) {
> DEFINE_WAIT(wait);
>
> if (rpmflags & (RPM_ASYNC | RPM_NOWAIT)) {
> retval = -EINPROGRESS;
> goto out;
> }
>
> /* Wait for the other suspend running in parallel with us. */
> for (;;) {
>
> The reason is above my horizon, although RPM_ASYNC looks suspicious.
> In general, we are re-entering rpm_suspend from within the driver
> handler, so the exit condition of rpm_suspend may not have been
> satisfied yet.
Ah yes, I vaguely remember thinking that another part would have to be
fixed. But it's not just the part you identified; the error actually
occurred higher up. The patch below ought to help.
Alan Stern
drivers/base/power/runtime.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
Index: usb-3.1/drivers/base/power/runtime.c
===================================================================
--- usb-3.1.orig/drivers/base/power/runtime.c
+++ usb-3.1/drivers/base/power/runtime.c
@@ -278,8 +278,9 @@ static int rpm_callback(int (*cb)(struct
* @rpmflags: Flag bits.
*
* Check if the device's runtime PM status allows it to be suspended. If
- * another suspend has been started earlier, either return immediately or wait
- * for it to finish, depending on the RPM_NOWAIT and RPM_ASYNC flags. Cancel a
+ * another suspend has been started earlier and the RPM_ASYNC flag isn't set,
+ * either return immediately or wait for it to finish, depending on the
+ * RPM_NOWAIT flag. Cancel a
* pending idle notification. If the RPM_ASYNC flag is set then queue a
* suspend request; otherwise run the ->runtime_suspend() callback directly.
* If a deferred resume was requested while the callback was running then carry
@@ -311,8 +312,7 @@ static int rpm_suspend(struct device *de
goto out;
/* If the autosuspend_delay time hasn't expired yet, reschedule. */
- if ((rpmflags & RPM_AUTO)
- && dev->power.runtime_status != RPM_SUSPENDING) {
+ if (rpmflags & RPM_AUTO) {
unsigned long expires = pm_runtime_autosuspend_expiration(dev);
if (expires != 0) {
@@ -339,10 +339,16 @@ static int rpm_suspend(struct device *de
/* Other scheduled or pending requests need to be canceled. */
pm_runtime_cancel_pending(dev);
- if (dev->power.runtime_status == RPM_SUSPENDING) {
+ /*
+ * If the request is synchronous, wait for a concurrent suspend attempt
+ * to finish. Allow asynchronous requests to go through; they will be
+ * cancelled if the concurrent suspend succeeds.
+ */
+ if (dev->power.runtime_status == RPM_SUSPENDING &&
+ !(rpmflags & RPM_ASYNC)) {
DEFINE_WAIT(wait);
- if (rpmflags & (RPM_ASYNC | RPM_NOWAIT)) {
+ if (rpmflags & RPM_NOWAIT) {
retval = -EINPROGRESS;
goto out;
}
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