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From: David Schwartz on 12 Nov 2009 17:31
On Nov 12, 9:46 am, 001 <snthib...(a)gmail.com> wrote:

> full buffer
>  804755 [unknown (0x3C4)] prodcons 2620 _cygtls::handle_exceptions:
> Error while
> dumping state (probably corrupted stack)
> Segmentation fault (core dumped)

Looks like you're corrupting the stack. How is 'buffer' allocated? Are
you sure you aren't accessing it out of bounds?

DS
From: 001 on 12 Nov 2009 19:32
On 12 nov, 23:31, David Schwartz <dav...(a)webmaster.com> wrote:
> On Nov 12, 9:46 am, 001 <snthib...(a)gmail.com> wrote:
>
> > full buffer
> >  804755 [unknown (0x3C4)] prodcons 2620 _cygtls::handle_exceptions:
> > Error while
> > dumping state (probably corrupted stack)
> > Segmentation fault (core dumped)
>
> Looks like you're corrupting the stack. How is 'buffer' allocated? Are
> you sure you aren't accessing it out of bounds?
>
> DS

Yup, you're right I was accessing that out of bounds too! I really
ought to watch out for those things, sorry for bothering you for these
stupid mistakes. Of course I ran into a lot of other problems again
after that :P, but I'll stop now... I think I can handle them.

Thanks!

Sincerely,

Stéphane
From: Chris M. Thomasson on 12 Nov 2009 12:16
"001" <snthibaud(a)gmail.com> wrote in message
news:8d8af023-15f3-4d5e-8cf9-f0a01d3bd4f8(a)l2g2000yqd.googlegroups.com...
> I tried to make a producer of 'items' but my implementation crashes
> at
> pthread_cond_wait ... I really tried looking at everything and put
> print statements throughout my code, but there it just crashes. I did
> put the wait within a mutex. This code isn't complete, but the
> relevant parts are in there (I assume). Any idea what I did wrong?
> This is the first time I used condition variables. Oh yeah... another
> question: is it possible to wait on multiple condition variables (and
> continue when one of them changes)? So that I can stop a thread
> independent of whether or not it is waiting for something?

[...]


FWIW, you can do a very simple bounded circular buffer like:


// pseudo-code typed in news reader.
___________________________________________________________________
#define DEPTH 8192


struct foo
{
char blah[128];
};


struct data
{
int in_use;
struct foo foo;
};


struct cbuf
{
struct data buffer[DEPTH]; /* = { { 0 } } */
size_t head; /* = 0 */
size_t tail; /* = 0 */
pthread_mutex_t mutex;
pthread_cond_t cond;
};


void
cbuf_push(struct cbuf* self,
struct foo const* f)
{
size_t i;

pthread_mutex_lock(&self->mutex);

i = (self->head++) % DEPTH;

while (self->buffer[i].in_use)
{
pthread_cond_wait(&self->cond, &self->mutex);
}

self->buffer[i].foo = *f;

self->buffer[i].in_use = 1;

pthread_mutex_unlock(&self->mutex);

pthread_cond_broadcast(&self->cond);
}


void
cbuf_pop(struct cbuf* self,
struct foo* f)
{
size_t i;

pthread_mutex_lock(&self->mutex);

i = (self->tail++) % DEPTH;

while (! self->buffer[i].in_use)
{
pthread_cond_wait(&self->cond, &self->mutex);
}

*f = self->buffer[i].foo;

self->buffer[i].in_use = 0;

pthread_mutex_unlock(&self->mutex);

pthread_cond_broadcast(&self->cond);
}
___________________________________________________________________




There ya go.

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