This is the mail archive of the
cygwin-developers@cygwin.com
mailing list for the Cygwin project.
RFC: TLS problem
- From: Thomas Pfaff <tpfaff at gmx dot net>
- To: cygwin-developers at cygwin dot com
- Date: Thu, 1 Aug 2002 16:48:09 +0200 (Westeuropäische Sommerzeit)
- Subject: RFC: TLS problem
While tracking down the problems with a threaded perl i recognized a
problem with TLS that is probably the reason for the forked child crash:
The TLS is not synced between parent and child. If i run my test program
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <stdio.h>
int main(void)
{
int w_key = TlsAlloc ();
TlsSetValue (w_key, (void*) 0x10);
switch (fork())
{
case -1:
return 0;
case 0:
printf ("child : %p\n", TlsGetValue (w_key));
break;
default:
wait (NULL);
printf ("parent: %p\n", TlsGetValue (w_key));
}
return 0;
}
i get
child : 0x0
parent: 0x10
Since perl use TLS (pthread keys to be true, but this will be mapped to
win32 TLS) to store the perl interpreter reference the child will crash
because the reference is NULL.
IMHO the are two possible solutions:
1. Synchronize the win32 TLS array between parent and child.
2. Create a cygwin only solution that will use its own tls array like CGFs
experimental TLS implementation.
I would prefer solution 1 because it will more general, consider that a
cygwin app can use the WIN32 TLS functions and not the pthread ones.
Thomas