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SubjectRe: [PATCH] PM: Prevent waiting forever on asynchronous suspend after abort
On Tue, 19 Jun 2012, Mandeep Singh Baines wrote:

> __device_suspend() must always send a completion. Otherwise, parent
> devices will wait forever.
>
> Commit 1e2ef05b, "PM: Limit race conditions between runtime PM and
> system sleep (v2)", introduced a regression by short-circuiting the
> complete_all() for certain error cases.
>
> This patch fixes the bug by always signalling a completion.
>
> Addresses http://crosbug.com/31972
>
> Tested by injecting an abort via the following patch:
>
> diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
> index a004db3..e5a6fce 100644
> --- a/drivers/usb/core/hcd-pci.c
> +++ b/drivers/usb/core/hcd-pci.c
> @@ -21,6 +21,7 @@
> #include <linux/pci.h>
> #include <linux/usb.h>
> #include <linux/usb/hcd.h>
> +#include <linux/string.h>
>
> #include <asm/io.h>
> #include <asm/irq.h>
> @@ -477,6 +478,8 @@ static int resume_common(struct device *dev, int event)
>
> static int hcd_pci_suspend(struct device *dev)
> {
> + if (!strcmp("0000:00:1d.3", dev_name(dev)))
> + return -EBUSY;
> return suspend_common(dev, device_may_wakeup(dev));
> }

When you include one patch in front of another like this, doesn't it
confuse the automatic tools? You might end up getting both changes
include in the final commit. :-)

> drivers/base/power/main.c | 6 ++++--
> 1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index e0fb5b0..9cb845e 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1031,7 +1031,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
> dpm_wait_for_children(dev, async);
>
> if (async_error)
> - return 0;
> + goto Complete;
>
> pm_runtime_get_noresume(dev);
> if (pm_runtime_barrier(dev) && device_may_wakeup(dev))
> @@ -1040,7 +1040,7 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
> if (pm_wakeup_pending()) {
> pm_runtime_put_sync(dev);
> async_error = -EBUSY;
> - return 0;
> + goto Complete;
> }
>
> device_lock(dev);
> @@ -1097,6 +1097,8 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async)
> }
>
> device_unlock(dev);
> +
> + Complete:
> complete_all(&dev->power.completion);
>
> if (error) {

Otherwise this looks right to me.

Acked-by: Alan Stern <stern@rowland.harvard.edu>



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