On 03/31/11 15:50, Kelly Anderson wrote:
Just to let you know. I'm using a gtx460 also. I haven't had a chance to reboot into the newly patched kernel yet. It is interesting that we both have gtx460's. I have a machine with a gtx430 that doesn't seem to exhibit the problem.
cat /etc/modprobe.d/snd_hda_intel.conf
options snd-hda-intel probe_mask=-1,0xa
OK, I debugged the problem and came up with a solution. The bottom line is that it's a problem with a signed to unsigned compare. First the fix:
--- ./sound/core/pcm_lib.c.orig 2011-03-27 12:37:20.000000000 -0600 +++ ./sound/core/pcm_lib.c 2011-03-31 19:01:35.392739127 -0600 @@ -379,17 +379,17 @@ static int snd_pcm_update_hw_ptr0(struct * Without regular period interrupts, we have to check * the elapsed time to detect xruns. */ - jdelta = jiffies - runtime->hw_ptr_jiffies; - if (jdelta < runtime->hw_ptr_buffer_jiffies / 2) + jdelta = (snd_pcm_sframes_t)(jiffies - runtime->hw_ptr_jiffies); + if (jdelta < (snd_pcm_sframes_t)runtime->hw_ptr_buffer_jiffies / 2) goto no_delta_check; hdelta = jdelta - delta * HZ / runtime->rate; - while (hdelta > runtime->hw_ptr_buffer_jiffies / 2 + 1) { + while (hdelta > (snd_pcm_sframes_t)runtime->hw_ptr_buffer_jiffies / 2 + 1) { delta += runtime->buffer_size; hw_base += runtime->buffer_size; if (hw_base >= runtime->boundary) hw_base = 0; new_hw_ptr = hw_base + pos; - hdelta -= runtime->hw_ptr_buffer_jiffies; + hdelta -= (snd_pcm_sframes_t)runtime->hw_ptr_buffer_jiffies; } goto no_delta_check; }
And here's the patch I used to debug the problem:
--- ./sound/core/pcm_lib.c.orig 2011-03-27 12:37:20.000000000 -0600 +++ ./sound/core/pcm_lib.c 2011-03-31 18:44:23.701411841 -0600 @@ -379,18 +379,31 @@ static int snd_pcm_update_hw_ptr0(struct * Without regular period interrupts, we have to check * the elapsed time to detect xruns. */ + int loopCount = 0; + BUG_ON(runtime->hw_ptr_jiffies < 0); + BUG_ON(runtime->hw_ptr_jiffies == 0); + BUG_ON(runtime->hw_ptr_jiffies > jiffies); jdelta = jiffies - runtime->hw_ptr_jiffies; if (jdelta < runtime->hw_ptr_buffer_jiffies / 2) goto no_delta_check; hdelta = jdelta - delta * HZ / runtime->rate; - while (hdelta > runtime->hw_ptr_buffer_jiffies / 2 + 1) { + printk(KERN_INFO "Before loop: jdelta=%ld, hdelta=%ld runtime->hw_ptr_buffer_jiffies=%lu\n" + , jdelta , hdelta , runtime->hw_ptr_buffer_jiffies); + while (hdelta > runtime->hw_ptr_buffer_jiffies / 2 + 1) { delta += runtime->buffer_size; hw_base += runtime->buffer_size; if (hw_base >= runtime->boundary) hw_base = 0; new_hw_ptr = hw_base + pos; - hdelta -= runtime->hw_ptr_buffer_jiffies; + hdelta -= runtime->hw_ptr_buffer_jiffies; + if (++loopCount >= 1024*1024*4) + { + printk(KERN_INFO "stopped the madness at 4 thousand\n"); + break; + } } + printk(KERN_INFO "After loop: jdelta=%ld, hdelta=%ld runtime->hw_ptr_buffer_jiffies=%lu\n" + , jdelta , hdelta , runtime->hw_ptr_buffer_jiffies); goto no_delta_check; }
The kernel output with the testing patch applied:
Mar 31 18:37:02 speedy kernel: Before loop: jdelta=352, hdelta=352 runtime->hw_ptr_buffer_jiffies=371 Mar 31 18:37:02 speedy kernel: stopped the madness at 4 million Mar 31 18:37:02 speedy kernel: After loop: jdelta=352, hdelta=-1556086432 runtime->hw_ptr_buffer_jiffies=371