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ipc: remove unnecessary comp_driver_list spinlock #10861

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ipc: remove unnecessary comp_driver_list spinlock #10861

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c3db875
ipc: ipc4: helper: drop redundant locking in ipc4_search_for_drv()
kv2019i Mar 31, 2026
4fcddd7
audio: component: drop redundant locking in driver list
kv2019i Jun 15, 2026
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14 changes: 7 additions & 7 deletions src/audio/component.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,23 +45,24 @@ DECLARE_TR_CTX(comp_tr, SOF_UUID(component_uuid), LOG_LEVEL_INFO);
int comp_register(struct comp_driver_info *drv)
{
struct comp_driver_list *drivers = comp_drivers_get();
k_spinlock_key_t key;

key = k_spin_lock(&drivers->lock);
/*
* No locking needed: the driver list is only modified at FW boot,
* where module init runs serially on the primary core, and at
* runtime from the serialized IPC thread (library load). These
* never overlap, so concurrent modification is not possible.
*/
list_item_prepend(&drv->list, &drivers->list);
k_spin_unlock(&drivers->lock, key);

return 0;
}

void comp_unregister(struct comp_driver_info *drv)
{
struct comp_driver_list *drivers = comp_drivers_get();
k_spinlock_key_t key;

key = k_spin_lock(&drivers->lock);
/* see comp_register() on why no locking is needed */
list_item_del(&drv->list);
k_spin_unlock(&drivers->lock, key);
}

int comp_set_adapter_ops(const struct comp_driver *drv, const struct module_interface *ops)
Expand Down Expand Up @@ -190,7 +191,6 @@ void sys_comp_init(struct sof *sof)
sof->comp_drivers = platform_shared_get(&cd, sizeof(cd));

list_init(&sof->comp_drivers->list);
k_spinlock_init(&sof->comp_drivers->lock);
}

void comp_get_copy_limits(struct comp_buffer *source,
Expand Down
1 change: 0 additions & 1 deletion src/include/sof/audio/component_ext.h
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,6 @@
/** \brief Holds list of registered components' drivers */
struct comp_driver_list {
struct list_item list; /**< list of component drivers */
struct k_spinlock lock; /**< list lock */
};

/** \brief Retrieves the component device buffer list. */
Expand Down
10 changes: 4 additions & 6 deletions src/ipc/ipc3/helper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,6 @@ static const struct comp_driver *get_drv(struct sof_ipc_comp *comp)
struct comp_driver_info *info;
struct sof_ipc_comp_ext *comp_ext;
uintptr_t offset;
k_spinlock_key_t key;

/* do we have extended data ? */
if (!comp->ext_data_length) {
Expand Down Expand Up @@ -127,9 +126,10 @@ static const struct comp_driver *get_drv(struct sof_ipc_comp *comp)
goto out;
}

/* search driver list with UUID */
key = k_spin_lock(&drivers->lock);

/*
* search driver list with UUID; no locking needed as the driver
* list is only modified at boot and from the serialized IPC thread
*/
list_for_item(clist, &drivers->list) {
info = container_of(clist, struct comp_driver_info,
list);
Expand All @@ -148,8 +148,6 @@ static const struct comp_driver *get_drv(struct sof_ipc_comp *comp)
*(uint32_t *)(&comp_ext->uuid[8]),
*(uint32_t *)(&comp_ext->uuid[12]));

k_spin_unlock(&drivers->lock, key);

out:
if (drv)
tr_dbg(&comp_tr, "get_drv(), found driver type %d, uuid %pU",
Expand Down
4 changes: 0 additions & 4 deletions src/ipc/ipc4/helper.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1142,12 +1142,9 @@ __cold static const struct comp_driver *ipc4_search_for_drv(const void *uuid)
struct list_item *clist;
const struct comp_driver *drv = NULL;
struct comp_driver_info *info;
uint32_t flags;

assert_can_be_cold();

irq_local_disable(flags);

/* search driver list with UUID */
list_for_item(clist, &drivers->list) {

@lyakh lyakh Jun 10, 2026

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looking at other locations, where the driver list is manipulated, we find 3 cases in component.c in functions like comp_register(). And there the list is protected by a dedicated spin-lock (as is the right way to do that). But if we now decide that it needs no protection, maybe we can remove those too. Or maybe make ipc4_get_comp_drv() a syscall and have it take this lock too?

@kv2019i kv2019i Jun 10, 2026

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Perhaps @lyakh but this PR is still valid, right?

@lyakh lyakh Jun 12, 2026

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Perhaps @lyakh but this PR is still valid, right?

@kv2019i sorry, but I tend to reason "no." It is the same driver list, so locking it on one flow and not locking it at another one doesn't seem correct. At the very least I'd put next to one or more of these locations a huge red warning, but those tend to be left unaddressed for years...

@kv2019i kv2019i Jun 12, 2026

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Fair enough, back to draft, I study other options.

@kv2019i kv2019i Jun 22, 2026

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Now removed the lock from all places (in V2 patchset pushed today).

info = container_of(clist, struct comp_driver_info,
Expand All @@ -1162,7 +1159,6 @@ __cold static const struct comp_driver *ipc4_search_for_drv(const void *uuid)
}
}

irq_local_enable(flags);
return drv;
}

Expand Down
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