/tmp 目录中文件的 futex：操作不允许

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.6 LTS
Release:    20.04
Codename:   focal

$ uname -r
5.15.0-125-generic

我正在尝试使用 Emacs 和 proof general 使用 snap 安装的 coq 定理证明助手。不幸的是，我遇到了错误。在使用 strace 进行调查后，我发现错误是由futex程序尝试处理目录中的文件时系统调用“权限被拒绝”引起的/tmp：

$ strace coqdep /tmp/ProofGeneral-coqofYWUP.v

trying to imitate what proof general does and got the following:

--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=123729, si_uid=1000} ---
rt_sigreturn({mask=[]})                 = 22
getpid()                                = 123729
tgkill(123729, 123751, SIGURG)          = 0
getpid()                                = 123729
tgkill(123729, 123750, SIGURG)          = 0
futex(0x55610de9d158, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x55610de9d250, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=100000}) = 0
getpid()                                = 123729
tgkill(123729, 123751, SIGURG)          = 0
getpid()                                = 123729
tgkill(123729, 123750, SIGURG)          = 0
futex(0x55610de9d158, FUTEX_WAKE_PRIVATE, 1) = 1
getpid()                                = 123729
tgkill(123729, 123751, SIGURG)          = 0
futex(0x55610de9d158, FUTEX_WAKE_PRIVATE, 1) = 1
epoll_pwait(4, [], 128, 0, NULL, 0)     = 0
futex(0xc000100948, FUTEX_WAKE_PRIVATE, 1) = 1
futex(0x55610de9d250, FUTEX_WAIT_PRIVATE, 0, {tv_sec=0, tv_nsec=100000}) = 0
close(3)                                = 0
futex(0x55610de9bc28, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
epoll_pwait(4, [{EPOLLOUT, {u32=1967093352, u64=140516117149288}}], 128, 0, NULL, 0) = 1
epoll_pwait(4, [{EPOLLOUT, {u32=1967093352, u64=140516117149288}}], 128, -1, NULL, 0) = 1
epoll_pwait(4, [], 128, 0, NULL, 191668) = 0
futex(0x55610de9bc28, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
epoll_pwait(4, [{EPOLLIN|EPOLLOUT, {u32=1967093592, u64=140516117149528}}], 128, 0, NULL, 0) = 1
epoll_pwait(4, [{EPOLLOUT, {u32=1967093352, u64=140516117149288}}], 128, -1, NULL, 0) = 1
epoll_pwait(4, [], 128, 0, NULL, 191668) = 0
epoll_pwait(4, [{EPOLLIN|EPOLLOUT, {u32=1967093352, u64=140516117149288}}], 128, -1, NULL, 0) = 1
recvmsg(3, {msg_name={sa_family=AF_UNIX, sun_path="/run/user/1000/bus"}, msg_namelen=112->21, msg_iov=[{iov_base="l\2\1\1'\0\0\0l\4\0\0-\0\0\0", iov_len=16}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 16
recvmsg(3, {msg_name={sa_family=AF_UNIX, sun_path="/run/user/1000/bus"}, msg_namelen=112->21, msg_iov=[{iov_base="\5\1u\0\2\0\0\0\6\1s\0\6\0\0\0:1.155\0\0\10\1g\0\1o\0\0"..., iov_len=48}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 48
recvmsg(3, {msg_name={sa_family=AF_UNIX, sun_path="/run/user/1000/bus"}, msg_namelen=112->21, msg_iov=[{iov_base="\"\0\0\0/org/freedesktop/systemd1/jo"..., iov_len=39}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 39
futex(0xc000100948, FUTEX_WAKE_PRIVATE, 1) = 1
recvmsg(3, {msg_namelen=112}, MSG_CMSG_CLOEXEC) = -1 EAGAIN (Resource temporarily unavailable)
openat(AT_FDCWD, "/proc/123729/cgroup", O_RDONLY|O_CLOEXEC) = 8
epoll_ctl(4, EPOLL_CTL_ADD, 8, {EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, {u32=1967093592, u64=140516117149528}}) = -1 EPERM (Operation not permitted)
read(8, "13:cpuset:/\n12:rdma:/\n11:memory:"..., 4096) = 547
close(8)                                = 0
write(6, "\0", 1)                       = 1
futex(0x55610de9bc28, FUTEX_WAIT_PRIVATE, 0, NULL) = 0
epoll_pwait(4, [], 128, 0, NULL, 0)     = 0
epoll_pwait(4,  <unfinished ...>)       = ?
*** Error: /tmp/ProofGeneral-coqofYWUP.v: No such file or directory
+++ exited with 1 +++

• 不幸的是，我没有足够的资格去理解是什么原因导致系统调用权限被拒绝。我甚至把这个文件的权限设为 777，但还是没用。

• 将文件复制到我的主目录后，它开始工作：

$ cp /tmp/ProofGeneral-coqofYWUP.v ~/aaa.v
$ coqdep ~/aaa.v
home/usr345/aaa.vo /home/usr345/aaa.glob /home/usr345/aaa.v.beautified /home/usr345/aaa.required_vo: /home/usr345/aaa.v 
/home/usr345/aaa.vio: /home/usr345/aaa.v