01-02-2009
So finally I want to close this thread with my conclusion concerning this problem.
It seems to be a problem of Linux. That is what someone told me in another newsgroup. He tried to implement a user-lever thread library for Linux, too, but ran into similar problems. His suggestions was to use pthreads or another OS (it should work fine in NetBSD). He posted also a link to the GNU FAQ for the C library, where they mention that it's not possible to do context switching in the signal handler. Here is the link:
Frequently Asked Questions about the GNU C Library
That's my conclusion. I hope this answers all questions concerning this thread.
Thread can be closed.
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LEARN ABOUT REDHAT
setcontext
GETCONTEXT(2) Linux Programmer's Manual GETCONTEXT(2)
NAME
getcontext, setcontext - get or set the user context
SYNOPSIS
#include <ucontext.h>
int getcontext(ucontext_t *ucp);
int setcontext(const ucontext_t *ucp);
where:
ucp points to a structure defined in <ucontext.h> containing the signal mask, execution stack, and machine registers.
DESCRIPTION
getcontext(2) gets the current context of the calling process, storing it in the ucontext struct pointed to by ucp.
setcontext(2) sets the context of the calling process to the state stored in the ucontext struct pointed to by ucp. The struct must either
have been created by getcontext(2) or have been passed as the third parameter of the sigaction(2) signal handler.
The ucontext struct created by getcontext(2) is defined in <ucontext.h> as follows:
typedef struct ucontext
{
unsigned long int uc_flags;
struct ucontext *uc_link;
stack_t uc_stack;
mcontext_t uc_mcontext;
__sigset_t uc_sigmask;
struct _fpstate __fpregs_mem;
} ucontext_t;
RETURN VALUES
getcontext(2) returns 0 on success and -1 on failure. setcontext(2) does not return a value on success and returns -1 on failure.
STANDARDS
These functions comform to: XPG4-UNIX.
NOTES
When a signal handler executes, the current user context is saved and a new context is created by the kernel. If the calling process
leaves the signal handler using longjmp(2), the original context cannot be restored, and the result of future calls to getcontext(2) are
unpredictable. To avoid this problem, use siglongjmp(2) or setcontext(2) in signal handlers instead of longjmp(2).
SEE ALSO
sigaction(2), sigaltstack(2), sigprocmask(2), sigsetjmp(3), setjmp(3).
Red Hat Linux 6.1 20 September 1999 GETCONTEXT(2)