| Message ID | 1628625938-149376-1-git-send-email-psodagud@codeaurora.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] PM: sleep: core: Avoid setting power.must_resume to false | expand |
On Tue, Aug 10, 2021 at 01:05:38PM -0700, Prasad Sodagudi wrote: > There are variables(power.may_skip_resume and dev->power.must_resume) > and DPM_FLAG_MAY_SKIP_RESUME flags to control the resume of devices after > a system wide suspend transition. > > Setting the DPM_FLAG_MAY_SKIP_RESUME flag means that the driver allows > its "noirq" and "early" resume callbacks to be skipped if the device > can be left in suspend after a system-wide transition into the working > state. PM core determines that the driver's "noirq" and "early" resume > callbacks should be skipped or not with dev_pm_skip_resume() function by > checking power.may_skip_resume variable. > > power.must_resume variable is getting set to false in __device_suspend() > function without checking device's DPM_FLAG_MAY_SKIP_RESUME and > dev->power.usage_count variables. In problematic scenario, where > all the devices in the suspend_late stage are successful and some > device can fail to suspend in suspend_noirq phase. So some devices > successfully suspended in suspend_late stage are not getting chance > to execute __device_suspend_noirq() to set dev->power.must_resume > variable to true and not getting resumed in early_resume phase. > > Add a check for device's DPM_FLAG_MAY_SKIP_RESUME flag before > setting power.must_resume variable in __device_suspend function. > > Fixes: 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase") > Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org> > --- > V2 -> V3: Format issues patch posting > V1 -> V2: Fixed indentation and commit text to include scenario > drivers/base/power/main.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index d568772..9ee6987 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -1642,7 +1642,11 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async) > } > > dev->power.may_skip_resume = true; > - dev->power.must_resume = false; > + if ((atomic_read(&dev->power.usage_count) <= 1) && > + (dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME))) > + dev->power.must_resume = false; > + else > + dev->power.must_resume = true; Again, what happens if the usage_count changes right after reading the value? What protects that from happening? thanks, greg k-h
On 2021-08-13 00:23, Greg KH wrote: > On Tue, Aug 10, 2021 at 01:05:38PM -0700, Prasad Sodagudi wrote: >> There are variables(power.may_skip_resume and dev->power.must_resume) >> and DPM_FLAG_MAY_SKIP_RESUME flags to control the resume of devices >> after >> a system wide suspend transition. >> >> Setting the DPM_FLAG_MAY_SKIP_RESUME flag means that the driver allows >> its "noirq" and "early" resume callbacks to be skipped if the device >> can be left in suspend after a system-wide transition into the working >> state. PM core determines that the driver's "noirq" and "early" resume >> callbacks should be skipped or not with dev_pm_skip_resume() function >> by >> checking power.may_skip_resume variable. >> >> power.must_resume variable is getting set to false in >> __device_suspend() >> function without checking device's DPM_FLAG_MAY_SKIP_RESUME and >> dev->power.usage_count variables. In problematic scenario, where >> all the devices in the suspend_late stage are successful and some >> device can fail to suspend in suspend_noirq phase. So some devices >> successfully suspended in suspend_late stage are not getting chance >> to execute __device_suspend_noirq() to set dev->power.must_resume >> variable to true and not getting resumed in early_resume phase. >> >> Add a check for device's DPM_FLAG_MAY_SKIP_RESUME flag before >> setting power.must_resume variable in __device_suspend function. >> >> Fixes: 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the >> resume phase") >> Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org> >> --- >> V2 -> V3: Format issues patch posting >> V1 -> V2: Fixed indentation and commit text to include scenario >> drivers/base/power/main.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c >> index d568772..9ee6987 100644 >> --- a/drivers/base/power/main.c >> +++ b/drivers/base/power/main.c >> @@ -1642,7 +1642,11 @@ static int __device_suspend(struct device *dev, >> pm_message_t state, bool async) >> } >> >> dev->power.may_skip_resume = true; >> - dev->power.must_resume = false; >> + if ((atomic_read(&dev->power.usage_count) <= 1) && >> + (dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME))) >> + dev->power.must_resume = false; >> + else >> + dev->power.must_resume = true; > > Again, what happens if the usage_count changes right after reading the > value? What protects that from happening? Hi Gregh KH, Yes. you are right. I think, relying on the usage_count at the __device_suspend stage may not be correct. Devices IRQs are still enabled and usage_count can be changed even after reading. I will send next patchset without power.usage_count check. @@ -1649,7 +1651,10 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async) } dev->power.may_skip_resume = true; - dev->power.must_resume = false; + if (dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME)) + dev->power.must_resume = false; + else + dev->power.must_resume = true; > > thanks, > > greg k-h
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index d568772..9ee6987 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -1642,7 +1642,11 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async) } dev->power.may_skip_resume = true; - dev->power.must_resume = false; + if ((atomic_read(&dev->power.usage_count) <= 1) && + (dev_pm_test_driver_flags(dev, DPM_FLAG_MAY_SKIP_RESUME))) + dev->power.must_resume = false; + else + dev->power.must_resume = true; dpm_watchdog_set(&wd, dev); device_lock(dev);
There are variables(power.may_skip_resume and dev->power.must_resume) and DPM_FLAG_MAY_SKIP_RESUME flags to control the resume of devices after a system wide suspend transition. Setting the DPM_FLAG_MAY_SKIP_RESUME flag means that the driver allows its "noirq" and "early" resume callbacks to be skipped if the device can be left in suspend after a system-wide transition into the working state. PM core determines that the driver's "noirq" and "early" resume callbacks should be skipped or not with dev_pm_skip_resume() function by checking power.may_skip_resume variable. power.must_resume variable is getting set to false in __device_suspend() function without checking device's DPM_FLAG_MAY_SKIP_RESUME and dev->power.usage_count variables. In problematic scenario, where all the devices in the suspend_late stage are successful and some device can fail to suspend in suspend_noirq phase. So some devices successfully suspended in suspend_late stage are not getting chance to execute __device_suspend_noirq() to set dev->power.must_resume variable to true and not getting resumed in early_resume phase. Add a check for device's DPM_FLAG_MAY_SKIP_RESUME flag before setting power.must_resume variable in __device_suspend function. Fixes: 6e176bf8d461 ("PM: sleep: core: Do not skip callbacks in the resume phase") Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org> --- V2 -> V3: Format issues patch posting V1 -> V2: Fixed indentation and commit text to include scenario drivers/base/power/main.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)