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5a8bee63b1
If a fuse filesystem is mounted inside a container, there is a problem during pid namespace destruction. The scenario is: 1. task (a thread in the fuse server, with a fuse file open) starts exiting, does exit_signals(), goes into fuse_flush() -> wait 2. fuse daemon gets killed, tries to wake everyone up 3. task from 1 is stuck because complete_signal() doesn't wake it up, since it has PF_EXITING. The result is that the thread will never be woken up, and pid namespace destruction will block indefinitely. To add insult to injury, nobody is waiting for these return codes, since the pid namespace is being destroyed. To fix this, let's not block on flush operations when the current task has PF_EXITING. This does change the semantics slightly: the wait here is for posix locks to be unlocked, so the task will exit before things are unlocked. To quote Miklos: "remote" posix locks are almost never used due to problems like this, so I think it's safe to do this. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Tycho Andersen <tycho@tycho.pizza> Link: https://lore.kernel.org/all/YrShFXRLtRt6T%2Fj+@risky/ Tested-by: Tycho Andersen <tycho@tycho.pizza> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.