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use rwlock for accessing ENV

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This commit is contained in:
The8472
2021-02-06 22:38:16 +01:00
parent cfba499271
commit 55ca27faa7
3 changed files with 55 additions and 11 deletions
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16
library/std/src/sys/unix/os.rs
View File

@@ -22,6 +22,7 @@ use crate::str;
use crate::sys::cvt;
use crate::sys::fd;
use crate::sys_common::mutex::{StaticMutex, StaticMutexGuard};
use crate::sys_common::rwlock::{RWLock, RWLockGuard};
use crate::vec;
use libc::{c_char, c_int, c_void};
@@ -493,17 +494,16 @@ pub unsafe fn environ() -> *mut *const *const c_char {
&mut environ
}
pub unsafe fn env_lock() -> StaticMutexGuard {
// It is UB to attempt to acquire this mutex reentrantly!
static ENV_LOCK: StaticMutex = StaticMutex::new();
ENV_LOCK.lock()
pub unsafe fn env_rwlock(readonly: bool) -> RWLockGuard {
static ENV_LOCK: RWLock = RWLock::new();
if readonly { ENV_LOCK.read_with_guard() } else { ENV_LOCK.write_with_guard() }
}
/// Returns a vector of (variable, value) byte-vector pairs for all the
/// environment variables of the current process.
pub fn env() -> Env {
unsafe {
let _guard = env_lock();
let _guard = env_rwlock(true);
let mut environ = *environ();
let mut result = Vec::new();
if !environ.is_null() {
@@ -540,7 +540,7 @@ pub fn getenv(k: &OsStr) -> io::Result<Option<OsString>> {
// always None as well
let k = CString::new(k.as_bytes())?;
unsafe {
let _guard = env_lock();
let _guard = env_rwlock(true);
let s = libc::getenv(k.as_ptr()) as *const libc::c_char;
let ret = if s.is_null() {
None
@@ -556,7 +556,7 @@ pub fn setenv(k: &OsStr, v: &OsStr) -> io::Result<()> {
let v = CString::new(v.as_bytes())?;
unsafe {
let _guard = env_lock();
let _guard = env_rwlock(false);
cvt(libc::setenv(k.as_ptr(), v.as_ptr(), 1)).map(drop)
}
}
@@ -565,7 +565,7 @@ pub fn unsetenv(n: &OsStr) -> io::Result<()> {
let nbuf = CString::new(n.as_bytes())?;
unsafe {
let _guard = env_lock();
let _guard = env_rwlock(false);
cvt(libc::unsetenv(nbuf.as_ptr())).map(drop)
}
}

6
library/std/src/sys/unix/process/process_unix.rs
View File

@@ -47,7 +47,7 @@ impl Command {
// a lock any more because the parent won't do anything and the child is
// in its own process.
let result = unsafe {
let _env_lock = sys::os::env_lock();
let _env_lock = sys::os::env_rwlock(true);
cvt(libc::fork())?
};
@@ -124,7 +124,7 @@ impl Command {
// Similar to when forking, we want to ensure that access to
// the environment is synchronized, so make sure to grab the
// environment lock before we try to exec.
let _lock = sys::os::env_lock();
let _lock = sys::os::env_rwlock(true);
let Err(e) = self.do_exec(theirs, envp.as_ref());
e
@@ -404,7 +404,7 @@ impl Command {
cvt_nz(libc::posix_spawnattr_setflags(attrs.0.as_mut_ptr(), flags as _))?;
// Make sure we synchronize access to the global `environ` resource
let _env_lock = sys::os::env_lock();
let _env_lock = sys::os::env_rwlock(true);
let envp = envp.map(|c| c.as_ptr()).unwrap_or_else(|| *sys::os::environ() as *const _);
cvt_nz(libc::posix_spawnp(
&mut p.pid,