On Mon, 17 Jun 2002, Jaroslav Kysela wrote:
> Bellow patch should fix this problem, but I need to do more tests with
> latest 2.5 and older 2.2 kernels, if it's a correct fix.
Hmm, this doesn't solve the problem at least when using the 2.4.17
kernel. With the test program I still get the assertation.
snd_pcm_mmap_data_open() is called right after fork() is called. And
then snd_pcm_data_close() is called with the pid of the
forked child. This seems a bit strange to me - why does a user-space
fork() cause a vmops open() in parent, and vmops close() in the child.
Anyways, after the fork() is done and snd_pcm_close() gets called in the
parent, snd_pcm_data_close() is called again in pcm_native.c.
This means that with the below patch mmap_count gets incremented once,
but decremented twice and so the assertion fails.
> Index: pcm_native.c
> ===================================================================
> RCS file: /cvsroot/alsa/alsa-kernel/core/pcm_native.c,v
> retrieving revision 1.13
> diff -u -r1.13 pcm_native.c
> --- pcm_native.c 23 May 2002 08:20:38 -0000 1.13
> +++ pcm_native.c 17 Jun 2002 10:21:21 -0000
> @@ -2573,16 +2573,16 @@
>
> static void snd_pcm_mmap_data_open(struct vm_area_struct *area)
> {
> -#if 0
> snd_pcm_substream_t *substream = (snd_pcm_substream_t *)area->vm_private_data;
> atomic_inc(&substream->runtime->mmap_count);
> -#endif
> + printk("mmap_data_open!!!\n");
> }
>
> static void snd_pcm_mmap_data_close(struct vm_area_struct *area)
> {
> snd_pcm_substream_t *substream = (snd_pcm_substream_t *)area->vm_private_data;
> atomic_dec(&substream->runtime->mmap_count);
> + printk("mmap_data_close!!!\n");
> }
>
> #ifndef LINUX_2_2
> @@ -2674,6 +2674,7 @@
> #ifdef VM_RESERVED
> area->vm_flags |= VM_RESERVED;
> #endif
> + printk("mmaping data!!!\n");
> atomic_inc(&runtime->mmap_count);
> return 0;
> }
>
>
> >
> > --cut--
> > #include <assert.h>
> > #include <stdio.h>
> > #include <sys/types.h>
> > #include <unistd.h>
> > #include <alsa/asoundlib.h>
> >
> > int main(int argc, char* argv[])
> > {
> > snd_pcm_t *handle;
> > snd_pcm_hw_params_t* hwparams;
> > int n, pid;
> >
> > int err = snd_pcm_open(&handle, "default",
> > SND_PCM_STREAM_PLAYBACK,
> > SND_PCM_NONBLOCK);
> > assert(err == 0);
> >
> > err += snd_pcm_hw_params_malloc(&hwparams);
> > err += snd_pcm_hw_params_any(handle, hwparams);
> > err += snd_pcm_hw_params(handle, hwparams);
> > assert(err == 0);
> >
> > pid = fork();
> > if (pid == 0) { /* child */
> > fprintf(stderr, "child pid=%d.\n", getpid());
> > exit(1);
> > }
> > else { /* parent */
> > fprintf(stderr, "parent pid=%d.\n", getpid());
> > sleep(1);
> >
> > snd_pcm_close(handle);
> > }
> > }
> > --cut---
> >
> > --
> > http://www.eca.cx
> > Audio software for Linux!
> >
> >
> > _______________________________________________________________
--
http://www.eca.cx
Audio software for Linux!
----------------------------------------------------------------------------
Bringing you mounds of caffeinated joy
>>> http://thinkgeek.com/sf <<<
_______________________________________________
Alsa-devel mailing list
[EMAIL PROTECTED]
https://lists.sourceforge.net/lists/listinfo/alsa-devel
