On 12 September 2013 01:43, Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: > If update_policy_cpu() is invoked with the existing policy->cpu itself > as the new-cpu parameter, then a lot of things can go terribly wrong. > > In its present form, update_policy_cpu() always assumes that the new-cpu > is different from policy->cpu and invokes other functions to perform their > respective updates. And those functions implement the actual update like > this: > > per_cpu(..., new_cpu) = per_cpu(..., last_cpu); > per_cpu(..., last_cpu) = NULL; > > Thus, when new_cpu == last_cpu, the final NULL assignment makes the per-cpu > references vanish into thin air! (memory leak). From there, it leads to more > problems: cpufreq_stats_create_table() now doesn't find the per-cpu reference > and hence tries to create a new sysfs-group; but sysfs already had created > the group earlier, so it complains that it cannot create a duplicate filename. > In short, the repercussions of a rather innocuous invocation of > update_policy_cpu() can turn out to be pretty nasty. > > Ideally update_policy_cpu() should handle this situation (new == last) > gracefully, and not lead to such severe problems. So fix it by adding an > appropriate check. > > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> > Tested-by: Stephen Warren <swarren@xxxxxxxxxx> > --- > > drivers/cpufreq/cpufreq.c | 3 +++ > 1 file changed, 3 insertions(+) We don't need this patch for the reasons that I outlined in other thread. We should never call this routine when cpu == policy->cpu -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
