Hi, My box can work well before suspend/resume. But it will complain the following warning message after suspend/resume. >[1266874868.022103] Enabling non-boot CPUs ... [1266874868.022198] BUG: soft lockup - CPU#0 stuck for 0s! [kthreadd:2] At the same time after I add the boot option of "printk.time=1", I find that the log time is changed spontaneously from 76 to 1266874868. > [ 76.475266] CPU3 is down [ 76.475312] Extended CMOS year: 2000 [1266874868.020631] x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106 [1266874868.021779] Back to C! [1266874868.022003] CPU0: Thermal LVT vector (0xfa) already installed [1266874868.022060] Extended CMOS year: 2000 More detailed info can be found in the attached file of dmesg_after_origin. After I look at the source code, I find that on this box the TSC runs at constant rate with P/T states and does not stop in deep C-states. And then the sched_clock_stable is set to 1. In such case the TSC time is used directly in the function of sched_clock_cpu. Then I do another test on this box, in which the clock_stable flag is saved/restored in course of suspend/resume(I add this by using per-cpu structure). When entering the suspended state, the clock_stable will be cleared. And when the system is resumed, the clock_stable will be set again. But unfortunately the soft lockup still exists. The file of dmesg_after_test2 is the dmesg log after I save/restore the clock_stable flag in course of suspend/resume. How about clearing the sched_clock_stable flag even when TSC doesn't stop in deep C-state? From my test it seems that the TSC value is unknown after doing suspend/resume. Thanks. Yakui.