On 30 July 2013 04:25, Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> wrote: > To perform light-weight cpu-init and teardown in the cpufreq subsystem > during suspend/resume, we need to separate out the 2 main functionalities > of the cpufreq CPU hotplug callbacks, as outlined below: > > 1. Init/tear-down of core cpufreq and CPU-specific components, which are > critical to the correct functioning of the cpufreq subsystem. > > 2. Init/tear-down of cpufreq sysfs files during suspend/resume. > > The first part requires accurate updates to the policy structure such as > its ->cpus and ->related_cpus masks, whereas the second part requires that > the policy->kobj structure is not released or re-initialized during > suspend/resume. > > To handle both these requirements, we need to allow updates to the policy > structure throughout suspend/resume, but prevent the structure from getting > freed up. Also, we must have a mechanism by which the cpu-up callbacks can > restore the policy structure, without allocating things afresh. (That also > helps avoid memory leaks). > > To achieve this, we use 2 schemes: > a. Use a fallback per-cpu storage area for preserving the policy structures > during suspend, so that they can be restored during resume appropriately. > > b. Use the 'frozen' flag to determine when to free or allocate the policy > structure vs when to restore the policy from the saved fallback storage. > Thus we can successfully preserve the structure across suspend/resume. > > Effectively, this helps us complete the separation of the 'light-weight' > and the 'full' init/tear-down sequences in the cpufreq subsystem, so that > this can be made use of in the suspend/resume scenario. > > Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com> > --- > > drivers/cpufreq/cpufreq.c | 69 > +++++++++++++++++++++++++++++++++++---------- > 1 file changed, 53 insertions(+), 16 deletions(-) >
Acked-by: Viresh Kumar <viresh.ku...@linaro.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
