On Tuesday, September 06, 2011, Tejun Heo wrote: > Hello, again. > > On Mon, Sep 05, 2011 at 11:15:12PM +0900, Tejun Heo wrote: > > > Freezing of tasks failed after 20.01 seconds (2 tasks refusing to freeze, wq_busy=0): > > > invert_cpu_stat D 0000000000000000 5304 20435 17329 0x00000084 > > > ffff8801f367bab8 0000000000000046 ffff8801f367bfd8 00000000001d3a00 > > > ffff8801f367a010 00000000001d3a00 00000000001d3a00 00000000001d3a00 > > > ffff8801f367bfd8 00000000001d3a00 ffff880414cc6840 ffff8801f36783c0 > > > Call Trace: > > > [<ffffffff81532de5>] schedule_timeout+0x235/0x320 > > > [<ffffffff81532a0b>] wait_for_common+0x11b/0x170 > > > [<ffffffff81532b3d>] wait_for_completion+0x1d/0x20 > > > [<ffffffff81364486>] _request_firmware+0x156/0x2c0 > > > [<ffffffff81364686>] request_firmware+0x16/0x20 > > > [<ffffffffa01f0da0>] request_microcode_fw+0x70/0xf0 [microcode] > > > [<ffffffffa01f0390>] microcode_init_cpu+0xc0/0x100 [microcode] > > > [<ffffffffa01f14b4>] mc_cpu_callback+0x7c/0x11f [microcode] > > > [<ffffffff815393a4>] notifier_call_chain+0x94/0xd0 > > > [<ffffffff8109770e>] __raw_notifier_call_chain+0xe/0x10 > > > [<ffffffff8106d000>] __cpu_notify+0x20/0x40 > > > [<ffffffff8152cf5b>] _cpu_up+0xc7/0x10e > > > [<ffffffff8152d07b>] cpu_up+0xd9/0xec > > > [<ffffffff8151e599>] store_online+0x99/0xd0 > > > [<ffffffff81355eb0>] sysdev_store+0x20/0x30 > > > [<ffffffff811f3096>] sysfs_write_file+0xe6/0x170 > > > [<ffffffff8117ee50>] vfs_write+0xd0/0x1a0 > > > [<ffffffff8117f024>] sys_write+0x54/0xa0 > > > [<ffffffff8153df02>] system_call_fastpath+0x16/0x1b > > > > So, this task is trying to bring a CPU up, which triggers firmware > > helper to load microcode. Firmware class currently sleeps > > non-interruptibly to wait for firmware load to complete, which is > > performed by another userland task. Now, the PM freezer doesn't > > assume that there will be non-freezable wait dependencies among > > userland tasks. It only knows two levels - userland and kernel tasks > > - and assumes that the former group may have non-freezable wait > > dependency on the latter but there's no such dependency among each > > group itself. If there's such dependency, PM freezer may fail, which > > is what happened here. > > > > ie. the firmware loader userland process got frozen first. > > invert_cpu_stat trying to bring up CPU was waiting for the firmware > > loader to finish in non-interruptible sleep, so the freezer couldn't > > proceed. > > Hmmm... I went through the code again and usermodehelper_disable() > seems to be there to prevent deadlocks like this. usermode helpers > are drained & plugged before freezing is tried. Rafael, the above > shouldn't be happening, right? No, it shouldn't in theory, but I'm not sure any more after the recent modifications of firmware loading related to the initialization. I'll have a closer look tomorrow. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
