Messages in this thread | | | Subject | Re: [Question] about patch: don't use [delayed_]work_pending() | From | qiaozhou <> | Date | Fri, 2 Sep 2016 09:17:04 +0800 |
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On 2016年09月02日 02:45, Tejun Heo wrote: > Hello, > > On Thu, Sep 01, 2016 at 05:09:36PM +0800, qiaozhou wrote: >> In our system, we do cpu clock init in of_clk_init path, and use pm qos to >> maintain cpu/cci clock. Firstly we init a CCI_CLK_QOS and set a default >> value, then update CCI_CLK_QOS to limit CCI min frequency according to >> current cpu frequency. Before calling pm_qos_update_request, irq is >> disabled, but after the calling, irq is enabled in cancel_delayed_work_sync, >> which causes some inconvenience before Before this patch is applied, it >> checks pending work and won't do cancel_delayed_work_sync in this boot up >> phase. > So, cancel_delayed_work_sync() usually shouldn't be called with irq > disabled as it's a possibly blocking call. Agree. > >> The simple calling sequence is like this: >> >> start_kernel -> of_clk_init -> cpu_clk_init -> pm_qos_add_request(xx, >> default_value), >> >> then pm_qos_update_request. >> >> I don't know whether it's meaningful to still check pending work here, or >> it's not suggested to use pm_qos_update_request in this early boot up phase. >> Could you help to share some opinions? (I can fix this issue by adding the >> current qos value directly instead of default value, though.) > Hmmm... but I suppose this is super-early in the boot. Would it make > sense to have a static variable (e.g. bool clk_fully_initailized) to > gate the cancel_delayed_sync() call? You're right that it's indeed super-early stage. But currently we can't control the gate of can_delayed_work_sync, since it's inside pm_qos_update_request. Out of our control. We can choose to not call pm_qos_update_request to avoid this issue, and use pm_qos_add_request alternatively. Good to have it. Thanks a lot.
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