add description to IntelliJ-patches.md

Author: vsalavatov

IntelliJ-patches.md

@@ -1,2 +1,20 @@
 # Included IntelliJ-related patches
-- TODO
+
+## `runBlocking` without Dispatcher starvation 
+
+[IJPL-721](https://youtrack.jetbrains.com/issue/IJPL-721), [#3983](https://github.com/Kotlin/kotlinx.coroutines/issues/3983)
+
+### Description:
+`runBlocking` with its default semantics may cause dispatcher starvation if it is called on a worker thread. 
+For example, if `runBlocking` happens to block all `Dispatchers.Default` workers, it may lead to a deadlock in the application:
+there may be tasks in the CPU queue that `runBlocking`s await, but there are none CPU workers available to run them.
+
+This patch changes the behavior of `runBlocking` so that it always releases associated computation permits before it parks,
+and reacquires them after unpark. It works for every `CoroutineDispatcher` that is built using library primitives:
+plain `Dispatcher.*` objects or `.limitedParallelism` limited dispatchers that are on top of them.
+
+This change in behavior comes with a cost. Permit reacquiring mechanism _may_ need an additional thread park/unpark.
+Worker threads that release their computational permits always let go of the local task queue, which means less benefit
+from locality, higher contention and transactional costs at the very least. 
+
+This patch doesn't change the fact that `runBlocking` should still be used carefully.