Re: INFO: task hung in pipe_read (2)

2020-08-13 Thread Tetsuo Handa
On 2020/08/13 16:00, Tetsuo Handa wrote: > On 2020/08/11 4:29, Andrea Arcangeli wrote: >> However once the mutex is killable there's no concern anymore and the >> hangcheck timer is correct also not reporting any misbehavior anymore. > > Do you mean something like below untested patch? I think tha

Re: INFO: task hung in pipe_read (2)

2020-08-13 Thread Tetsuo Handa
On 2020/08/11 4:29, Andrea Arcangeli wrote: > However once the mutex is killable there's no concern anymore and the > hangcheck timer is correct also not reporting any misbehavior anymore. Do you mean something like below untested patch? I think that the difficult part is that mutex for close() op

Re: INFO: task hung in pipe_read (2)

2020-08-10 Thread Andrea Arcangeli
Hello Tetsuo, On Sat, Aug 08, 2020 at 10:01:21AM +0900, Tetsuo Handa wrote: > use of killable waits disables ability to detect possibility of deadlock > (because > lockdep can't check possibility of deadlock which involves actions in > userspace), for > syzkaller process is SIGKILLed after 5 sec

Re: INFO: task hung in pipe_read (2)

2020-08-07 Thread Tetsuo Handa
On 2020/08/07 14:31, Andrea Arcangeli wrote: >> Andrea? Comments? As mentioned, this is probably much too aggressive, >> but I do think we need to limit the time that the kernel will wait for >> page faults. > > Why is pipe preventing to SIGKILL the task that is blocked on the > mutex_lock? Is the

Re: INFO: task hung in pipe_read (2)

2020-08-06 Thread Andrea Arcangeli
Hello! On Sat, Aug 01, 2020 at 10:39:00AM -0700, Linus Torvalds wrote: > On Sat, Aug 1, 2020 at 8:30 AM Tetsuo Handa > wrote: > > > > Waiting for response at > > https://lkml.kernel.org/r/45a9b2c8-d0b7-8f00-5b30-0cfe3e028...@i-love.sakura.ne.jp > > . > > I think handle_userfault() should have

Re: INFO: task hung in pipe_read (2)

2020-08-01 Thread Linus Torvalds
On Sat, Aug 1, 2020 at 8:30 AM Tetsuo Handa wrote: > > Waiting for response at > https://lkml.kernel.org/r/45a9b2c8-d0b7-8f00-5b30-0cfe3e028...@i-love.sakura.ne.jp > . I think handle_userfault() should have a (shortish) timeout, and just return VM_FAULT_RETRY. The code is overly complex anyway

Re: INFO: task hung in pipe_read (2)

2020-08-01 Thread Tetsuo Handa
Waiting for response at https://lkml.kernel.org/r/45a9b2c8-d0b7-8f00-5b30-0cfe3e028...@i-love.sakura.ne.jp . #syz dup: INFO: task hung in pipe_write (4)

INFO: task hung in pipe_read (2)

2020-08-01 Thread syzbot
Hello, syzbot found the following issue on: HEAD commit:01830e6c Add linux-next specific files for 20200731 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=11b922e090 kernel config: https://syzkaller.appspot.com/x/.config?x=2e226b2d1364112c dashboard