[fuse-devel] Kernel Hung in FUSE

[Sargun D. <sa...@sa...>]

We have a FUSE daemon, and users that access them that run in a pid
namespace. When the pid namespace is torn down, we end up in a
situation where in userspace, a user gets stuck. Specifically, they
get stuck in request_wait_answer.

PID: 3655410  TASK: ffff8bc9f87ada00  CPU: 55  COMMAND: "mount.objective"
 #0 [ffffb12820137ca8] __schedule at ffffffffb5aecf8d
 #1 [ffffb12820137d40] schedule at ffffffffb5aed492
 #2 [ffffb12820137d50] request_wait_answer at ffffffffb558ec1a
 #3 [ffffb12820137da8] __fuse_request_send at ffffffffb558ff1f
 #4 [ffffb12820137dc8] fuse_readdir at ffffffffb5594022
 #5 [ffffb12820137e78] iterate_dir at ffffffffb548a1ae
 #6 [ffffb12820137eb8] __x64_sys_getdents at ffffffffb548ad29
 #7 [ffffb12820137f38] do_syscall_64 at ffffffffb5204185
 #8 [ffffb12820137f50] entry_SYSCALL_64_after_hwframe at ffffffffb5c00088
    RIP: 00007fdae2d888eb  RSP: 00007fdadcc9fcf0  RFLAGS: 00000206
    RAX: ffffffffffffffda  RBX: 00007fda840008f0  RCX: 00007fdae2d888eb
    RDX: 0000000000020000  RSI: 00007fda840008f0  RDI: 0000000000000040
    RBP: 00007fda840008f0   R8: 00007fda84000000   R9: 0000000000000001
    R10: 0000000000000000  R11: 0000000000000206  R12: 00007fdadcc9fe20
    R13: 00007fda840008c0  R14: 0000000000000000  R15: 00007fdae3ba7250
    ORIG_RAX: 000000000000004e  CS: 0033  SS: 002b

Is there a reason why at the end of request_wait_answer, it doesn't
wait_killable, and then when a fatal signal comes in, the request is
aborted, if it is not locked?