Author: jonpryor
Date: 2005-04-20 07:29:20 -0400 (Wed, 20 Apr 2005)
New Revision: 43324
Modified:
trunk/mcs/class/Mono.Posix/Mono.Unix/ChangeLog
trunk/mcs/class/Mono.Posix/Mono.Unix/Syscall.cs
Log:
* Syscall.cs: Make all fork(2) and exec(2) functions `private`. It
currently isn't safe to call these under *any* circumstances.
Modified: trunk/mcs/class/Mono.Posix/Mono.Unix/ChangeLog
===================================================================
--- trunk/mcs/class/Mono.Posix/Mono.Unix/ChangeLog 2005-04-20 11:16:05 UTC
(rev 43323)
+++ trunk/mcs/class/Mono.Posix/Mono.Unix/ChangeLog 2005-04-20 11:29:20 UTC
(rev 43324)
@@ -1,3 +1,31 @@
+2005-04-20 Jonathan Pryor <[EMAIL PROTECTED]>
+
+ * Syscall.cs: Make all fork(2) and exec(2) functions `private`. It
+ currently isn't safe to call these under *any* circumstances. See
also
+ 68141, and this pertinent quote from Butenhof's
+ "Programming with POSIX Threads", p197, s6.1:
+
+ "When a threaded process calls fork to create a child process,
+ Pthreads specifies that only the thread calling fork exists in the
+ child. ... Pthreads does not 'terminate' the other threads in a
forked
+ process...They simply cease to exist. ... This is not a problem
if
+ the child process is about to call exec to run a new program, but
if
+ you use fork to clone a threaded program, beware that you may lose
+ access to memory, especially heap memory stored only as
+ thread-specific data values."
+
+ Since P/Invoke currently requires using thread local storage, once you
+ fork(2) you won't be able to invoke exec(2) from managed code (since
that
+ would require a P/Invoke transition to call exec(2), which would
require
+ TLS, which doesn't exist in the new process).
+
+ This can only be fixed by removing the TLS dependency on P/Invoke,
which
+ isn't a priority (and may not be possible).
+
+ The workaround is to create a C function which does your
fork(2)/exec(2)
+ (and any other functions such as daemon(3)) on your behalf, and
P/Invoke
+ to call this C function.
+
2005-04-18 Jonathan Pryor <[EMAIL PROTECTED]>
* Syscall.cs: Update comment specifying which functions belong in
Syscall.
Modified: trunk/mcs/class/Mono.Posix/Mono.Unix/Syscall.cs
===================================================================
--- trunk/mcs/class/Mono.Posix/Mono.Unix/Syscall.cs 2005-04-20 11:16:05 UTC
(rev 43323)
+++ trunk/mcs/class/Mono.Posix/Mono.Unix/Syscall.cs 2005-04-20 11:29:20 UTC
(rev 43324)
@@ -2329,17 +2329,17 @@
// TODO: does Mono marshal arrays properly?
[DllImport (LIBC, SetLastError=true)]
- public static extern int execve (string path, string[] argv,
string[] envp);
+ private static extern int execve (string path, string[] argv,
string[] envp);
[DllImport (LIBC, SetLastError=true)]
- public static extern int fexecve (int fd, string[] argv,
string[] envp);
+ private static extern int fexecve (int fd, string[] argv,
string[] envp);
[DllImport (LIBC, SetLastError=true)]
- public static extern int execv (string path, string[] argv);
+ private static extern int execv (string path, string[] argv);
// TODO: execle, execl, execlp
[DllImport (LIBC, SetLastError=true)]
- public static extern int execvp (string path, string[] argv);
+ private static extern int execvp (string path, string[] argv);
[DllImport (LIBC, SetLastError=true)]
public static extern int nice (int inc);
@@ -2488,14 +2488,14 @@
[DllImport (LIBC, SetLastError=true)]
[Obsolete ("DO NOT directly call fork(2); it bypasses essential
" +
"shutdown code.\nUse System.Diagnostics.Process
instead")]
- public static extern int fork ();
+ private static extern int fork ();
// vfork(2)
// pid_t vfork(void);
[DllImport (LIBC, SetLastError=true)]
[Obsolete ("DO NOT directly call vfork(2); it bypasses
essential " +
"shutdown code.\nUse System.Diagnostics.Process
instead")]
- public static extern int vfork ();
+ private static extern int vfork ();
[DllImport (LIBC, SetLastError=true, EntryPoint="ttyname")]
private static extern IntPtr sys_ttyname (int fd);
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