Hi, I'm working on some particularly complex kernel hacking thing and I thought that I could use some input from more experienced guys and thought that LKML might not be a best place to ask this, while Kernelnewbies seems more appropriate, even thought I'm not entirely newbie. I'm dealing with a problem that my heavily modified system "hangs" while the vanilla does not. My version works fine, but at some point of booting process it stops. When I'm debugging the issue I can clearly see that scheduler is switching between swapper and kworker processes only, while other processes are sleeping: (gdb) ps 0xC09BFF10 0 Running - - (none) swapper 0xC786F280 1 Sleep(In.) - - (none) init 0xC786E960 2 Sleep(In.) - - (none) kthreadd 0xC786E040 3 Sleep(In.) - - (none) ksoftirqd/0 0xC78792A0 4 Running - - (none) kworker/0:0 0xC7878980 5 Sleep(In.) - - (none) kworker/u:0 0xC7878060 6 Sleep(In.) - - (none) cpuset 0xC78892C0 7 Sleep(In.) - - (none) khelper 0xC78889A0 8 Sleep(In.) - - (none) kworker/u:1 0xC7888080 277 Sleep(In.) - - (none) sync_supers 0xC789B2E0 279 Sleep(In.) - - (none) bdi-default 0xC78C1320 281 Sleep(In.) - - (none) kblockd 0xC78B1300 292 Sleep(In.) - - (none) ata_sff 0xC78C00E0 304 Sleep(Un.) - - (none) khubd 0xC78F1340 327 Sleep(In.) - - (none) kworker/0:1 0xC78F0A20 328 Sleep(In.) - - (none) cfg80211 0xC78F0100 411 Sleep(In.) - - (none) rpciod 0xC789A9C0 419 Sleep(In.) - - (none) khungtaskd 0xC78C0A00 420 Sleep(Un.) - - (none) kswapd0 0xC7927360 421 Sleep(In.) - - (none) fsnotify_mark 0xC78B00C0 422 Sleep(In.) - - (none) nfsiod 0xC7926A40 424 Sleep(In.) - - (none) crypto 0xC7A6CA80 523 Sleep(In.) - - (none) zd1211rw 0xC7926120 532 Sleep(In.) - - (none) libertastf 0xC7A64140 566 Sleep(In.) - - (none) kworker/0:2 0xC7A65380 573 Sleep(In.) - - (none) kpsmoused 0xC7A6D3A0 592 Sleep(In.) - - (none) kworker/u:2 0xC7A6C160 606 Sleep(In.) - - (none) mmcqd/0 0xC78B09E0 644 Sleep(In.) - - (none) jbd2/mmcblk0p2- 0xC7A9C1A0 645 Sleep(In.) - - (none) ext4-dio-unwrit 0xC7A64A60 647 Sleep(In.) - - (none) plymouthd 0xC789A0A0 649 Sleep(Un.) - - (none) plymouthd 0xC7A9D3E0 651 Sleep(Un.) - - (none) sh This is the output of macro that I'm using. (In.) == Interruptable; (Un.) == Uninterraptable The problem is: I don't entirely understand all the details about scheduling/task primitives and the problem can sit just anywhere: my changes touch the bare bones of exception handling etc. I wish to know: - what data structures and fields should I check to see if there are any pending signals - what all the stuff in scheduling data? - how would you approach such problem while being able to run two versions (modified and vanilla) side by side - what are critical functions in kernel code that are dealing with waking and putting processes into sleep; I wish to break debbugger on them or put some printk's here and there and look for some pattern Can you throw some ideas or links/books to read? Much appreciated. Best Regards, -- Dawid Ciężarkiewicz