Re: [PATCH] ALSA: pcm: Remove VLA usage

From: Takashi Sakamoto
Date: Tue Mar 13 2018 - 09:59:22 EST


Hi,

On Mar 13 2018 20:37, Takashi Iwai wrote:
A helper function used by snd_pcm_hw_refine() still keeps using VLA
for timestamps of hw constraint rules that are non-fixed size.

Let's replace the VLA with a simple kmalloc() array.

Reference: https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/core/pcm_native.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

Yeah. I have concerned about it for a long time but kept it as is because it had no issue. Now, let's obsolete it.

Reviewed-by: Takashi Sakamoto <o-takashi@xxxxxxxxxxxxx>

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 77ba50ddcf9e..756a9a3884a5 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -323,7 +323,7 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
struct snd_pcm_hw_constraints *constrs =
&substream->runtime->hw_constraints;
unsigned int k;
- unsigned int rstamps[constrs->rules_num];
+ unsigned int *rstamps;
unsigned int vstamps[SNDRV_PCM_HW_PARAM_LAST_INTERVAL + 1];
unsigned int stamp;
struct snd_pcm_hw_rule *r;
@@ -331,7 +331,7 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
struct snd_mask old_mask;
struct snd_interval old_interval;
bool again;
- int changed;
+ int changed, err = 0;
/*
* Each application of rule has own sequence number.
@@ -339,8 +339,9 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
* Each member of 'rstamps' array represents the sequence number of
* recent application of corresponding rule.
*/
- for (k = 0; k < constrs->rules_num; k++)
- rstamps[k] = 0;
+ rstamps = kcalloc(constrs->rules_num, sizeof(unsigned int), GFP_KERNEL);
+ if (!rstamps)
+ return -ENOMEM;
/*
* Each member of 'vstamps' array represents the sequence number of
@@ -398,8 +399,10 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
}
changed = r->func(params, r);
- if (changed < 0)
- return changed;
+ if (changed < 0) {
+ err = changed;
+ goto out;
+ }
/*
* When the parameter is changed, notify it to the caller
@@ -430,7 +433,9 @@ static int constrain_params_by_rules(struct snd_pcm_substream *substream,
if (again)
goto retry;
- return 0;
+ out:
+ kfree(rstamps);
+ return err;
}
static int fixup_unreferenced_params(struct snd_pcm_substream *substream,


Thanks

Takashi Sakamoto