lkml.org 
[lkml]   [2020]   [Apr]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [GIT PULL] Please pull proc and exec work for 5.7-rc1
    On Thu, Apr 30, 2020 at 4:20 AM Linus Torvalds
    <torvalds@linux-foundation.org> wrote:
    > On Wed, Apr 29, 2020 at 6:08 PM Bernd Edlinger
    > <bernd.edlinger@hotmail.de> wrote:
    > >
    > > I added the BIG FAT WARNNIG comments as a mitigation for that.
    > > Did you like those comments?
    >
    > No.
    >
    > What's the point olf saying "THIS CODE IS GARBAGE" and then expecting
    > that to make it ok?
    >
    > No,m that doesn't make it ok. It just means that it should have been
    > done differently.
    >
    > > Yes, exactly, the point is the caller is expected to call wait in that
    > > scenario, otherwise the -EAGAIN just repeats forever, that is an API
    > > change, yes, but something unavoidable, and the patch tries hard to
    > > limit it to cases where the live-lock or pseudo-dead-lock is unavoidable
    > > anyway.
    >
    > I'm getting really fed up with your insistence on that KNOWN BROKEN
    > garbage test-case.
    >
    > It's shit. The test-case is wrong. I've told you before.
    >
    > Your patch as-is breaks other cases that are *not* wrong in the kernel
    > currently, and that don't have test-cases because they JustWork(tm).
    >
    > The livelock isn't interesting. The test-case that shows it is pure
    > garbage, and is written wrong.
    >
    > IF that test-case hadn't been buggy in the first place, it would have
    > had ignored its child (or had a handler for SIGCHLD), and not
    > livelocked.

    But if we go with Bernd's approach together with your restart
    suggestion, then simply doing PTRACE_ATTACH on two threads A and B
    would be enough to livelock, right?

    tracer: PTRACE_ATTACHes to A
    B: enters de_thread()
    tracer: attempts to PTRACE_ATTACH to B

    Now the tracer will loop on PTRACE_ATTACH, right?

    \
     
     \ /
      Last update: 2020-04-30 05:00    [W:5.058 / U:0.128 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site