Hi...
I run the (almost) latest -mm kernel (2.6.20-rc3-mm1), and see some strange behaviour
with POSIX threads (glibc-2.4).
I have downgraded my test to a simple textboox example for a SMP-safe spool
queue, it's just a circular queue with a mutex and a condition variable for in
and out. I have seen the same structure in several places.
Well, it just sometimes gets blocked. GDB says its stuck in pthread_wait().
I could swear it worked on previous kernels. It works as is on IRIX.
I will try to build an older kernel to test.
I takes a second to block it with something like while :; tst; done.
Any ideas ?
--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
Mandriva Linux release 2007.1 (Cooker) for i586
Linux 2.6.19-jam04 (gcc 4.1.2 20061110 (prerelease) (4.1.2-0.20061110.2mdv2007.1)) #0 SMP PREEMPT
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#define SIZE 16
int jobs[SIZE];
int in;
int slots;
pthread_mutex_t slots_mutex;
pthread_cond_t slots_cond;
int out;
int items;
pthread_mutex_t items_mutex;
pthread_cond_t items_cond;
void put(int job);
void get(int* job);
void* prod(void* data);
void* cons(void* data);
int main(int argc,char** argv)
{
pthread_t prodid,consid;
in = 0;
slots = SIZE;
pthread_mutex_init(&slots_mutex,0);
pthread_cond_init(&slots_cond,0);
out = 0;
items = 0;
pthread_mutex_init(&items_mutex,0);
pthread_cond_init(&items_cond,0);
pthread_setconcurrency(3);
pthread_create(&prodid,0,prod,0);
pthread_create(&consid,0,cons,0);
pthread_join(prodid,0);
pthread_join(consid,0);
return 0;
}
void* prod(void* data)
{
int i;
for (i=0; i<1000; i++)
{
if (!(i%100))
printf("put %d\n",i);
put(i);
}
put(-1);
puts("prod done");
return 0;
}
void* cons(void* data)
{
int i;
do
{
get(&i);
if (!(i%100))
printf("got %d\n",i);
}
while (i>=0);
puts("cons done");
return 0;
}
void put(int job)
{
pthread_mutex_lock(&slots_mutex);
while (slots<=0)
pthread_cond_wait(&slots_cond,&slots_mutex);
jobs[in] = job;
in++;
in %= SIZE;
slots--;
items++;
pthread_mutex_unlock(&slots_mutex);
pthread_mutex_lock(&items_mutex);
pthread_cond_signal(&items_cond);
pthread_mutex_unlock(&items_mutex);
}
void get(int* job)
{
pthread_mutex_lock(&items_mutex);
while (items<=0)
pthread_cond_wait(&items_cond,&items_mutex);
*job = jobs[out];
out++;
out %= SIZE;
items--;
slots++;
pthread_mutex_unlock(&items_mutex);
pthread_mutex_lock(&slots_mutex);
pthread_cond_signal(&slots_cond);
pthread_mutex_unlock(&slots_mutex);
}
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