# Objective
Fixes a possible deadlock between `AssetServer::get_asset_loader` / `AssetServer::add_loader`
A thread could take the `extension_to_loader_index` read lock,
and then have the `server.loader` write lock taken in add_loader
before it can. Then add_loader can't take the extension_to_loader_index
lock, and the program deadlocks.
To be more precise:
## Step 1: Thread 1 grabs the `extension_to_loader_index` lock on lines 138..139:
3a1867a92e/crates/bevy_asset/src/asset_server.rs (L133-L145)
## Step 2: Thread 2 grabs the `server.loader` write lock on line 107:
3a1867a92e/crates/bevy_asset/src/asset_server.rs (L103-L116)
## Step 3: Deadlock, since Thread 1 wants to grab `server.loader` on line 141...:
3a1867a92e/crates/bevy_asset/src/asset_server.rs (L133-L145)
... and Thread 2 wants to grab 'extension_to_loader_index` on lines 111..112:
3a1867a92e/crates/bevy_asset/src/asset_server.rs (L103-L116)
## Solution
Fixed by descoping the extension_to_loader_index lock, since
`get_asset_loader` doesn't need to hold the read lock on the extensions map for the duration,
just to get a copyable usize. The block might not be needed,
I think I could have gotten away with just inserting a `copied()`
call into the chain, but I wanted to make the reasoning clear for
future maintainers.
85a10eccc5