Hi. On pátek 24. listopadu 2017 11:22:28 CET Jean Delvare wrote: > 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
Tested and attached a couple of patches on top of those to the BZ. If disabling fan control is the only approach here, I can confirm that this works. Thanks. Regards, Oleksandr
