Hi Oleksandr, On jeu., 2017-11-23 at 22:41 +0100, Oleksandr Natalenko wrote: > I've noticed that querying Dell Vostro 3360 hwmon sensor freezes the system > completely (like, really completely, even mouse cursor does not move, and > sound playback stops) for approx. half of a second. Then, system recovers and > runs as usual. Also, sensor readings are okay, for instance: > > === > $ sensors dell_smm-virtual-0 > dell_smm-virtual-0 > Adapter: Virtual device > Processor Fan: 5615 RPM > CPU: +51.0°C > Ambient: +36.0°C > Other: +63.0°C > SODIMM: +41.0°C > === > > So, I've used trace-cmd to check what takes that much amount of time to > execute, and got this: > > === > # trace-cmd record -p function_graph -l i8k_smm -F sensors dell_smm-virtual-0 > $ trace-cmd report > ... > sensors-23694 [002] 89099.214369: funcgraph_entry: # 503440.746 us | > i8k_smm(); > ... > === > > Clearly, 0.5 s delay. > > Looking at i8k_smm(), it calls i8k_smm_func() on 0th CPU: > > === > 232 ret = smp_call_on_cpu(0, i8k_smm_func, regs, true); > === > > which, in turn, does some asm magic. > > I know that SMM is kinda "black box", and kernel has little to do with it, but > I think that under Windows, for instance, it would work without freezes. So, > likely, querying SMM might be done differently. > > I do not know how to approach this issue, thus asking for help/advice. Also, > CCing Jonathan since the comment before asm magic says this: > > === > 137 * Call the System Management Mode BIOS. Code provided by Jonathan > Buzzard. > === > > This was also reported in various places before, for instance, [1], but > unfortunately, without any solution. There are two patches waiting to be tested in https://bugzilla.kernel.org/show_bug.cgi?id=195751 -- Jean Delvare SUSE L3 Support -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
