Date: Sat, 25 Apr 1998 14:12:53 -0000 From: "=?KOI8-R?Q?=FB=C1=D4=C1=C5=D7_=E1=CC=C5=CB=D3=C1=CE=C4=D2?=" <div@nsu.ru> To: "Q:FreeBSD" <freebsd-questions@FreeBSD.ORG> Subject: pthread question Message-ID: <199804250712.OAA17632@mx.nsu.ru>
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Hi, all
I can not understand the reason of a problem with which I has met.
This problem consists in that that in multithread application
active thread with no system calls references does not allow
other threads to work. I can demonstrate it by attached test program.
The purpose of this test is a reception of external timer for active
thread which can has (in general) long periods of work without system
calls. Thus here is thread with blind infinite loop and initial thread
with loop of interval sleep (usleep/setitimer, nanosleep, select
timeout - no difference). On my system (2.2.6) initial thread creates
child thread and goes to sleep, there is the context switch to child
thread without return - child thread runs forever.
Little history. I develop some virtual machine as a kernel for
database engine. It runs some multithread (not a pthread) pseudocode
and uses external clock(SIGALRM/setitimer before) for context switching.
I'v used pthreads in this situation for my async IO system.
But after I have updated system (2.2.2 -> 2.2.6) there was the above
mentioned problem. Sometimes signals are lost sometimes signal handlers,
select timeout wait realisation of external clock was unsuccessfull.
If you will have ideas on this occassion I shall be rather glad to listen.
Beforehand grateful, Boris Muratshin.
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#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/signal.h>
#include <pthread.h>
#include <unistd.h>
extern "C" int nanosleep( const struct timespec* , struct timespec* );
void sigvt( int n)
{
printf("---%d",n);
fflush(0);
}
void *proc2( void*p )
{
for (;;)
{
for (int j=0;j<10000000;j++);
// printf("!");
// fflush(0);
// pthread_yield();
}
return NULL;
}
int main( )
{
struct timespec ts={0,10000000};
struct timeval tv={0,10000};
pthread_t thread2;
pthread_create(&thread2,NULL,proc2,"bbb");
for (;;)
{
printf("<");
fflush(0);
select(0,NULL,NULL,NULL,&tv);
// usleep(10000);
// nanosleep(&ts,NULL);
printf(">");
fflush(0);
}
return 0;
}
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