Re: [PATCH 2/8] PM / domains: Protect reading loop over list of domains

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From	Krzysztof Kozlowski <krzk@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/8] PM / domains: Protect reading loop over list of domains
Date	Mon, 12 Jun 2017 15:20:02 +0200
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On Mon, Jun 12, 2017 at 02:57:21PM +0200, Ulf Hansson wrote:
> On 9 June 2017 at 18:16, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> > On Fri, Jun 09, 2017 at 06:08:47PM +0200, Krzysztof Kozlowski wrote:
> >> The pm_genpd_present() iterates over list of domains so grabbing a
> >> gpd_list_lock mutex is necessary before calling it.  Otherwise we could
> >> end up in iterating over and modifying the list at the same time.
> >>
> >> Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> >> ---
> >>  drivers/base/power/domain.c | 7 ++++++-
> >>  1 file changed, 6 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> >> index 2e8d0f423507..2a6935dc0164 100644
> >> --- a/drivers/base/power/domain.c
> >> +++ b/drivers/base/power/domain.c
> >> @@ -1099,8 +1099,13 @@ static void genpd_syscore_switch(struct device *dev, bool suspend)
> >>       struct generic_pm_domain *genpd;
> >>
> >>       genpd = dev_to_genpd(dev);
> 
> Actually there may be potential problem here as we may end up trying
> to use the container_of() call for a PM domain, not being a genpd but
> something else.
> 
> >> -     if (!pm_genpd_present(genpd))
> >> +
> >> +     mutex_lock(&gpd_list_lock);
> >> +     if (!pm_genpd_present(genpd)) {
> >> +             mutex_unlock(&gpd_list_lock);
> >>               return;
> >> +     }
> >> +     mutex_unlock(&gpd_list_lock);
> 
> Perhaps convert the hole thing above to call genpd_lookup_dev() instead?

Indeed, that would solve both problems. Thanks, I'll fix this.

Best regards,
Krzysztof

Thread

[PATCH 0/8] PM / Domains: Bunch of small improvements and fixes Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:10 +0200
  [PATCH 1/8] PM / Domains: Constify genpd pointer Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:10 +0200
  [PATCH 2/8] PM / domains: Protect reading loop over list of domains Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:10 +0200
    Re: [PATCH 2/8] PM / domains: Protect reading loop over list of  domains Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:20 +0200
      Re: [PATCH 2/8] PM / domains: Protect reading loop over list of domains Ulf Hansson <ulf.hansson@linaro.org> - 2017-06-12 15:00 +0200
        Re: [PATCH 2/8] PM / domains: Protect reading loop over list of  domains Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-12 15:20 +0200
  [PATCH 5/8] PM / domains: Fix unsafe iteration over modified list of domain providers Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:10 +0200
  [PATCH 3/8] PM / domains: Add lockdep asserts for domains list mutex Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:20 +0200
  [PATCH 4/8] PM / domains: Fix unsafe iteration over modified list of device links Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:20 +0200
  [PATCH 7/8] PM / domains: Fix missing default_power_down_ok comment Krzysztof Kozlowski <krzk@kernel.org> - 2017-06-09 18:20 +0200

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