2013/6/13 Viresh Kumar <viresh.kumar@xxxxxxxxxx>: > On 13 June 2013 14:31, Xiaoguang Chen <chenxg@xxxxxxxxxxx> wrote: >> cpufreq governor stop and start should be kept in sequence. >> If not, there will be unexpected behavior, for example: >> >> we have 4 cpus and policy->cpu=cpu0, cpu1/2/3 are linked to cpu0. >> the normal sequence is as below: >> >> 1) Current governor is userspace, one application tries to set >> governor to ondemand. it will call __cpufreq_set_policy in which it >> will stop userspace governor and then start ondemand governor. >> >> 2) Current governor is userspace, now cpu0 hotplugs in cpu3, it will >> call cpufreq_add_policy_cpu. on which it first stops userspace >> governor, and then starts userspace governor. >> >> Now if the sequence of above two cases interleaves, it becames >> below sequence: >> >> 1) application stops userspace governor >> 2) hotplug stops userspace governor >> 3) application starts ondemand governor >> 4) hotplug starts a governor >> >> in step 4, hotplug is supposed to start userspace governor, but now >> the governor has been changed by application to ondemand, so hotplug >> starts ondemand governor again !!!! >> >> The solution is: do not allow stop one policy's governor multi-times >> Governor stop should only do once for one policy, after it is stopped, >> no other governor stop should be executed. also add one mutext to >> protect __cpufreq_governor so governor operation can be kept in sequence. >> >> Signed-off-by: Xiaoguang Chen <chenxg@xxxxxxxxxxx> >> --- >> drivers/cpufreq/cpufreq.c | 24 ++++++++++++++++++++++++ >> include/linux/cpufreq.h | 1 + >> 2 files changed, 25 insertions(+) > > I forgot to tell you earlier but please update changelog everytime you > send a new version. > > Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> Thanks I'll pay attention next time :) Xiaoguang -- 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
