On Mon, 26 Jun 2023 13:13:21 +0200,
Takashi Iwai wrote:
>
> On Mon, 26 Jun 2023 13:09:00 +0200,
> Jaroslav Kysela wrote:
> >
> > On 26. 06. 23 13:02, Takashi Iwai wrote:
> > > On Mon, 26 Jun 2023 09:56:47 +0200,
> > > Jaroslav Kysela wrote:
> > >>
> > >> On 26. 06. 23 9:33, Takashi Iwai wrote:
> > >>> On Mon, 26 Jun 2023 09:31:18 +0200,
> > >>> Tuo Li wrote:
> > >>>>
> > >>>>
> > >>>> Hello,
> > >>>>
> > >>>> Thank you for your reply!
> > >>>
> > >>> FWIW, the simplest fix would be something like below, just extending
> > >>> the mutex coverage. But it'll serialize the all calls, so it might
> > >>> influence on the performance, while it's the safest way.
> > >>
> > >> It may be better to update total_pcm_alloc_bytes before
> > >> snd_dma_alloc_dir_pages() call and decrease this value when allocation
> > >> fails to allow parallel allocations. Then the mutex can be held only
> > >> for the total_pcm_alloc_bytes variable update.
> > >
> > > Yes, it'd work. But a tricky part is that the actual allocation size
> > > can be bigger, and we need to correct the total_pcm_alloc_bytes after
> > > the allocation result. So the end result would be a patch like below,
> > > which is a bit more complex than the previous simpler approach. But
> > > it might be OK.
> >
> > The patch looks good, but it may be better to move the "post" variable
> > updates to an inline function (mutex lock - update - mutex unlock) for
> > a better readability.
>
> Sounds like a good idea. Let me cook later.
... and here it is.
If that looks OK, I'll submit a proper fix patch.
thanks,
Takashi
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -31,15 +31,41 @@ static unsigned long max_alloc_per_card = 32UL * 1024UL * 1024UL;
module_param(max_alloc_per_card, ulong, 0644);
MODULE_PARM_DESC(max_alloc_per_card, "Max total allocation bytes per card.");
+static void __update_allocated_size(struct snd_card *card, ssize_t bytes)
+{
+ card->total_pcm_alloc_bytes += bytes;
+}
+
+static void update_allocated_size(struct snd_card *card, ssize_t bytes)
+{
+ mutex_lock(&card->memory_mutex);
+ __update_allocated_size(card, bytes);
+ mutex_unlock(&card->memory_mutex);
+}
+
+static void decrease_allocated_size(struct snd_card *card, size_t bytes)
+{
+ mutex_lock(&card->memory_mutex);
+ WARN_ON(card->total_pcm_alloc_bytes < bytes);
+ __update_allocated_size(card, -(ssize_t)bytes);
+ mutex_unlock(&card->memory_mutex);
+}
+
static int do_alloc_pages(struct snd_card *card, int type, struct device *dev,
int str, size_t size, struct snd_dma_buffer *dmab)
{
enum dma_data_direction dir;
int err;
+ /* check and reserve the requested size */
+ mutex_lock(&card->memory_mutex);
if (max_alloc_per_card &&
- card->total_pcm_alloc_bytes + size > max_alloc_per_card)
+ card->total_pcm_alloc_bytes + size > max_alloc_per_card) {
+ mutex_unlock(&card->memory_mutex);
return -ENOMEM;
+ }
+ __update_allocated_size(card, size);
+ mutex_unlock(&card->memory_mutex);
if (str == SNDRV_PCM_STREAM_PLAYBACK)
dir = DMA_TO_DEVICE;
@@ -47,9 +73,14 @@ static int do_alloc_pages(struct snd_card *card, int type, struct device *dev,
dir = DMA_FROM_DEVICE;
err = snd_dma_alloc_dir_pages(type, dev, dir, size, dmab);
if (!err) {
- mutex_lock(&card->memory_mutex);
- card->total_pcm_alloc_bytes += dmab->bytes;
- mutex_unlock(&card->memory_mutex);
+ /* the actual allocation size might be bigger than requested,
+ * and we need to correct the account
+ */
+ if (dmab->bytes != size)
+ update_allocated_size(card, dmab->bytes - size);
+ } else {
+ /* take back on allocation failure */
+ decrease_allocated_size(card, size);
}
return err;
}
@@ -58,10 +89,7 @@ static void do_free_pages(struct snd_card *card, struct snd_dma_buffer *dmab)
{
if (!dmab->area)
return;
- mutex_lock(&card->memory_mutex);
- WARN_ON(card->total_pcm_alloc_bytes < dmab->bytes);
- card->total_pcm_alloc_bytes -= dmab->bytes;
- mutex_unlock(&card->memory_mutex);
+ decrease_allocated_size(card, dmab->bytes);
snd_dma_free_pages(dmab);
dmab->area = NULL;
}
