11-15-2010
Because that is the way the people who were developing the POSIX threads standard agreed to do it. These were the same people who developed actual POSIX threads implementations in operating systems.
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1. Programming
Here is simple code for multithreading in POSIX:
void* simplethread(void* arg)
{
printf("Hello World\n");
}
int main(void)
{
pthread_t id;
pthread_create(&id, NULL, simplethread, NULL);
return 0;
}
Whether the new thread will run or not depends on the OS. Tricky ... (5 Replies)
Discussion started by: _rocky
5 Replies
2. Programming
how to do with that?
after cc -o xxxx xxxx.c
ld:
Unresolved:
_pthread_create
_pthread_deteach
_pthread_exit
Thanks (3 Replies)
Discussion started by: zhshqzyc
3 Replies
3. Programming
Hello
My problem goes like this:
I have used Pthread_create, and I have tryed to create 2 proccess but nothing happens! It does not even matter what the function im trying to create do. It is if im trying to activate an empty function. This is my code.
Any help will be highly appreciated.... (1 Reply)
Discussion started by: Hellboy
1 Replies
4. Programming
Hi.
I use C++ and I wishes to create a thread with the pthread_create function, my question is, how can I do this if I wish that the function will be a member of the class ??
I know from windows programming that I can declare a static function like this
static unsigned int __stdcall... (7 Replies)
Discussion started by: shvalb
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5. Solaris
Im trying to run an application i compiled (iperf) and i get an error telling me that it cant create the pthread. when i ran the ./configuration one of the things it checked was for pthreads which came back ok.
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6. Programming
I try to compile a sample c code in fedora eclipse 3.2 as managed makefile using pthread library,it shows some error on pthread functions.Error is of undefined reference to pthread.Anybody guide me to solve this problem.
Thanking you (1 Reply)
Discussion started by: sujith4u87
1 Replies
7. Programming
Hi guys.
H was learning posix threads in C with anjuta IDE. it gives me
undefined reference to `pthread_create'
I know i should compile it like:
gcc -lpthread main.c
how should i import this configuration in anjuta so i can compile inside it? (2 Replies)
Discussion started by: majid.merkava
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8. UNIX for Dummies Questions & Answers
Hi,
I'm trying to do my homework assignment but I am having trouble using the pthread_create fucntion.
Here is my code________________
//Alicia Johnson
//sum_pid program
//creates n number of threads. These threads create a random number
//then adds the number to a global array. Then... (1 Reply)
Discussion started by: ajohns38
1 Replies
9. Programming
Suppose I have a simple program main() with a global varibale int x=0.
int x = 0;
main()
{
print("%d\n",x);
}
I want to create two threads/process which must access this variable x in sync.
Which one will be better threads( pthread_create ) or process( fork )?
If I go with fork() then... (1 Reply)
Discussion started by: rupeshkp728
1 Replies
NPTL(7) Linux Programmer's Manual NPTL(7)
NAME
nptl - Native POSIX Threads Library
DESCRIPTION
NPTL (Native POSIX Threads Library) is the GNU C library POSIX threads implementation that is used on modern Linux systems.
NPTL and signals
NPTL makes internal use of the first two real-time signals (signal numbers 32 and 33). One of these signals is used to support thread can-
cellation and POSIX timers (see timer_create(2)); the other is used as part of a mechanism that ensures all threads in a process always
have the same UIDs and GIDs, as required by POSIX. These signals cannot be used in applications.
To prevent accidental use of these signals in applications, which might interfere with the operation of the NPTL implementation, various
glibc library functions and system call wrapper functions attempt to hide these signals from applications, as follows:
* SIGRTMIN is defined with the value 34 (rather than 32).
* The sigwaitinfo(2), sigtimedwait(2), and sigwait(3) interfaces silently ignore requests to wait for these two signals if they are speci-
fied in the signal set argument of these calls.
* The sigprocmask(2) and pthread_sigmask(3) interfaces silently ignore attempts to block these two signals.
* The sigaction(2), pthread_kill(3), and pthread_sigqueue(3) interfaces fail with the error EINVAL (indicating an invalid signal number)
if these signals are specified.
* sigfillset(3) does not include these two signals when it creates a full signal set.
NPTL and process credential changes
At the Linux kernel level, credentials (user and group IDs) are a per-thread attribute. However, POSIX requires that all of the POSIX
threads in a process have the same credentials. To accommodate this requirement, the NPTL implementation wraps all of the system calls
that change process credentials with functions that, in addition to invoking the underlying system call, arrange for all other threads in
the process to also change their credentials.
The implementation of each of these system calls involves the use of a real-time signal that is sent (using tgkill(2)) to each of the other
threads that must change its credentials. Before sending these signals, the thread that is changing credentials saves the new creden-
tial(s) and records the system call being employed in a global buffer. A signal handler in the receiving thread(s) fetches this informa-
tion and then uses the same system call to change its credentials.
Wrapper functions employing this technique are provided for setgid(2), setuid(2), setegid(2), seteuid(2), setregid(2), setreuid(2), setres-
gid(2), setresuid(2), and setgroups(2).
CONFORMING TO
For details of the conformance of NPTL to the POSIX standard, see pthreads(7).
NOTES
POSIX says that any thread in any process with access to the memory containing a process-shared (PTHREAD_PROCESS_SHARED) mutex can operate
on that mutex. However, on 64-bit x86 systems, the mutex definition for x86-64 is incompatible with the mutex definition for i386, meaning
that 32-bit and 64-bit binaries can't share mutexes on x86-64 systems.
SEE ALSO
credentials(7), pthreads(7), signal(7), standards(7)
Linux 2015-08-08 NPTL(7)