On Sat, Apr 7, 2018 at 6:24 PM, Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> wrote: > Dmitry Vyukov wrote: >> On Sat, Apr 7, 2018 at 5:39 PM, Peter Zijlstra <pet...@infradead.org> wrote: >> > On Sat, Apr 07, 2018 at 09:31:19PM +0900, Tetsuo Handa wrote: >> >> are for replacing debug_show_all_locks() in check_hung_task() for cases >> >> like >> >> https://syzkaller.appspot.com/bug?id=26aa22915f5e3b7ca2cfca76a939f12c25d624db >> >> because we are interested in only threads holding locks. >> >> >> >> SysRq-t is too much but SysRq-w is useless for killable/interruptible >> >> threads... >> > >> > Or use a script to process the sysrq-t output? I mean, we can add all >> > sorts, but where does it end? > > Maybe allow khungtaskd to call call_usermode_helper() to run arbitrary > operations > instead of just calling panic()?
This would probably work for syzbot too. >> Good question. >> We are talking about few dozen more stacks, right? >> >> Not all kernel bugs are well reproducible, so it's not always possible >> to go back and hit sysrq-t. And this come up in the context of syzbot, >> which is an automated system. It reported a bunch of hangs and most of >> them are real bugs, but not all of them are easily actionable. >> Can it be a config or a command line argument, which will make syzbot >> capture more useful context for each such hang? >> > > It will be nice if syzbot testing is done with kdump configured, and the > result of automated scripting on vmcore (such as "foreach bt -s -l") is > available. kdump's popped up several times already (https://github.com/google/syzkaller/issues/491). But this will require some non-trivial amount of work to pipe it through the whole system (starting from investigation/testing, second kernel to storing them and exposing).