Messages in this thread | | | Date | Thu, 1 Mar 2018 21:24:02 +0000 | From | Mark Brown <> | Subject | Re: [PATCH v3 07/25] ASoC: qcom: qdsp6: Add support to Q6ADM |
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On Tue, Feb 13, 2018 at 04:58:19PM +0000, srinivas.kandagatla@linaro.org wrote:
> +static struct copp *adm_find_copp(struct q6adm *adm, int port_idx, > + int copp_idx) > +{ > + struct copp *c; > + > + spin_lock(&adm->copps_list_lock); > + list_for_each_entry(c, &adm->copps_list, node) { > + if ((port_idx == c->afe_port) && (copp_idx == c->copp_idx)) { > + spin_unlock(&adm->copps_list_lock); > + return c; > + } > + } > + > + spin_unlock(&adm->copps_list_lock);
We've again got this use of spinlocks here but no IRQ safety - what exactly is going on with the locking? In general all of the locking in this stuff is raising very serious alarm bells with me, I don't understand what is being protected against what and there's some very obvious bugs. We could probably use some documentation about what the locking is supposed to be doing.
> + case ADM_CMDRSP_DEVICE_OPEN_V5: {
> + copp->id = open->copp_id; > + wake_up(&copp->wait); > + } > + break; > + default:
This indentation is confusing.
> +static struct copp *adm_find_matching_copp(struct q6adm *adm, > + int port_id, int topology, > + int mode, int rate, int channel_mode, > + int bit_width, int app_type) > +{ > + struct copp *c; > + > + spin_lock(&adm->copps_list_lock); > + > + list_for_each_entry(c, &adm->copps_list, node) { > + if ((port_id == c->afe_port) && (topology == c->topology) && > + (mode == c->mode) && (rate == c->rate) && > + (bit_width == c->bit_width) && (app_type == c->app_type)) { > + spin_unlock(&adm->copps_list_lock); > + return c; > + } > + } > + spin_unlock(&adm->copps_list_lock); > + > + c = adm_alloc_copp(adm, port_id);
So really this is a find or allocate operation...
> + if (IS_ERR_OR_NULL(c)) > + return ERR_CAST(c); > + > + mutex_lock(&c->lock); > + c->refcnt = 0;
Why do we need to lock the thing we just allocated but didn't yet initialize, and surely if something can find it before we finished initializing we have a race condition?
> + copp = adm_find_matching_copp(adm, port_id, topology, perf_mode, > + rate, channel_mode, bit_width, app_type); > + > + /* Create a COPP if port id are not enabled */ > + if (copp->refcnt == 0) { > + ret = q6adm_device_open(adm, copp, port_id, path, topology, > + channel_mode, bit_width, rate); > + if (ret < 0) > + return ret; > + } > + mutex_lock(&copp->lock); > + copp->refcnt++; > + mutex_unlock(&copp->lock);
There's an obvious race here between checking the reference count and incrementing it - something might drop a reference before we increment it which would be bad. I'm also not clear when we'd want multiple things using a single COPP.
> + mutex_lock(&copp->lock); > + copp->refcnt--; > + mutex_unlock(&copp->lock); > + if (!copp->refcnt) {
This locking is also broken. [unhandled content-type:application/pgp-signature] | |