Possible pthread bug

[Andrew Walrond <andrew at walrond dot org>]

If I create a thread with pthread_create, and then immediately call
pthread_setschedparam to get a realtime thread, the fn returns 0
(success) but the thread doesn't get the higher priority. Interesting
the internally created pthread manager thread *does* get the higher
priority.

ps output
  F S   UID   PID  PPID  C PRI  NI ADDR    SZ WCHAN  TTY      CMD
100 R     0  1675  1621 99  85   0    -  2404 -      pts/1    threads
040 S     0  1676  1675  0  57   0    -  2404 schedu pts/1    threads
040 S     0  1677  1676  0  75   0    -  2404 schedu pts/1    threads

If I introduce a delay (with sleep) between creation and setschedparam,
it works fine.

ps output with sleep
  F S   UID   PID  PPID  C PRI  NI ADDR    SZ WCHAN  TTY      CMD
100 R     0  1664  1621 85  85   0    -  2404 -      pts/1    threads
040 S     0  1665  1664  0  57   0    -  2404 schedu pts/1    threads
040 S     0  1666  1665  0  58   0    -  2404 schedu pts/1    threads

Is this behavior correct?

I'm using glibc 2.2.5 with gcc 3.2 on RH7.3 (i386)

Simple example follows (gcc -o threads -lpthread threads.cpp)

#include <pthread.h>
#include <unistd.h>
#include <stdio.h>

void* ThreadFn(void* context)
{
	while (true) sleep(1);
}

int main(int argc,char* argv[])
{
	pthread_t tid;
	int res = pthread_create(&tid,0,ThreadFn,0);

	//sleep(1);

	sched_param sp;
	sp.sched_priority=1;
	res = pthread_setschedparam(tid,SCHED_RR,&sp);
	printf("pthread_setschedparam returned %d\n",res);

	while (true) sleep(0);

	return 0;
}