diff options
| -rw-r--r-- | drivers/hwtracing/stm/core.c | 54 |
1 files changed, 42 insertions, 12 deletions
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index f86f56d8535f..30181821d909 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -694,18 +694,26 @@ err_free: } EXPORT_SYMBOL_GPL(stm_register_device); -static void __stm_source_link_drop(struct stm_source_device *src, - struct stm_device *stm); +static int __stm_source_link_drop(struct stm_source_device *src, + struct stm_device *stm); void stm_unregister_device(struct stm_data *stm_data) { struct stm_device *stm = stm_data->stm; struct stm_source_device *src, *iter; - int i; + int i, ret; mutex_lock(&stm->link_mutex); list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) { - __stm_source_link_drop(src, stm); + ret = __stm_source_link_drop(src, stm); + /* + * src <-> stm link must not change under the same + * stm::link_mutex, so complain loudly if it has; + * also in this situation ret!=0 means this src is + * not connected to this stm and it should be otherwise + * safe to proceed with the tear-down of stm. + */ + WARN_ON_ONCE(ret); } mutex_unlock(&stm->link_mutex); @@ -824,22 +832,28 @@ fail_detach: * * Caller must hold stm::link_mutex. */ -static void __stm_source_link_drop(struct stm_source_device *src, - struct stm_device *stm) +static int __stm_source_link_drop(struct stm_source_device *src, + struct stm_device *stm) { struct stm_device *link; + int ret = 0; lockdep_assert_held(&stm->link_mutex); - if (src->data->unlink) - src->data->unlink(src->data); - /* for stm::link_list modification, we hold both mutex and spinlock */ spin_lock(&stm->link_lock); spin_lock(&src->link_lock); link = srcu_dereference_check(src->link, &stm_source_srcu, 1); - if (WARN_ON_ONCE(link != stm)) + + /* + * The linked device may have changed since we last looked, because + * we weren't holding the src::link_lock back then; if this is the + * case, tell the caller to retry. + */ + if (link != stm) { + ret = -EAGAIN; goto unlock; + } stm_output_free(link, &src->output); list_del_init(&src->link_entry); @@ -850,6 +864,11 @@ static void __stm_source_link_drop(struct stm_source_device *src, unlock: spin_unlock(&src->link_lock); spin_unlock(&stm->link_lock); + + if (!ret && src->data->unlink) + src->data->unlink(src->data); + + return ret; } /** @@ -865,18 +884,29 @@ unlock: static void stm_source_link_drop(struct stm_source_device *src) { struct stm_device *stm; - int idx; + int idx, ret; +retry: idx = srcu_read_lock(&stm_source_srcu); + /* + * The stm device will be valid for the duration of this + * read section, but the link may change before we grab + * the src::link_lock in __stm_source_link_drop(). + */ stm = srcu_dereference(src->link, &stm_source_srcu); + ret = 0; if (stm) { mutex_lock(&stm->link_mutex); - __stm_source_link_drop(src, stm); + ret = __stm_source_link_drop(src, stm); mutex_unlock(&stm->link_mutex); } srcu_read_unlock(&stm_source_srcu, idx); + + /* if it did change, retry */ + if (ret == -EAGAIN) + goto retry; } static ssize_t stm_source_link_show(struct device *dev, |