2.6.38-stable review patch. If anyone has any objections, please let us know.
------------------ From: Kelly Anderson <[email protected]> commit 12ff414e2e4512f59fe191dc18e856e2939a1c79 upstream. When period interrupts are disabled, snd_pcm_update_hw_ptr0() compares the current time against the time estimated for the current hardware pointer to detect xruns. The somewhat fuzzy threshold in the while loop makes it possible that hdelta becomes negative; the comparison being done with unsigned types then makes the loop go through the entire 263 negative range, and, depending on the value, never reach an unsigned value that is small enough to stop the loop. Doing this with interrupts disabled results in the machine locking up. To prevent this, ensure that the loop condition uses signed types for both operands so that the comparison is correctly done. Many thanks to Kelly Anderson for debugging this. Reported-by: Nix <[email protected]> Reported-by: "Christopher K." <[email protected]> Reported-and-tested-by: Kelly Anderson <[email protected]> Signed-off-by: Kelly Anderson <[email protected]> [cl: remove unneeded casts; use a temp variable] Signed-off-by: Clemens Ladisch <[email protected]> Signed-off-by: Takashi Iwai <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- sound/core/pcm_lib.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -375,6 +375,7 @@ static int snd_pcm_update_hw_ptr0(struct } if (runtime->no_period_wakeup) { + snd_pcm_sframes_t xrun_threshold; /* * Without regular period interrupts, we have to check * the elapsed time to detect xruns. @@ -383,7 +384,8 @@ static int snd_pcm_update_hw_ptr0(struct 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) { + xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1; + while (hdelta > xrun_threshold) { delta += runtime->buffer_size; hw_base += runtime->buffer_size; if (hw_base >= runtime->boundary) _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
