• Miklos Szeredi's avatar
    fuse: fix possibly missed wake-up after abort · 2d84a2d1
    Miklos Szeredi authored
    In current fuse_drop_waiting() implementation it's possible that
    fuse_wait_aborted() will not be woken up in the unlikely case that
    fuse_abort_conn() + fuse_wait_aborted() runs in between checking
    fc->connected and calling atomic_dec(&fc->num_waiting).
    
    Do the atomic_dec_and_test() unconditionally, which also provides the
    necessary barrier against reordering with the fc->connected check.
    
    The explicit smp_mb() in fuse_wait_aborted() is not actually needed, since
    the spin_unlock() in fuse_abort_conn() provides the necessary RELEASE
    barrier after resetting fc->connected.  However, this is not a performance
    sensitive path, and adding the explicit barrier makes it easier to
    document.
    Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
    Fixes: b8f95e5d ("fuse: umount should wait for all requests")
    Cc: <stable@vger.kernel.org> #v4.19
    2d84a2d1
dev.c 54 KB