Mention why we don't have pthread_cancel().
It's a somewhat frequently asked question.
Change-Id: I2ad88e8d79607e49a891eb2304e9be63494ad193
diff --git a/docs/status.md b/docs/status.md
index 5470668..fb88dd2 100644
--- a/docs/status.md
+++ b/docs/status.md
@@ -33,7 +33,11 @@
Missing functionality:
* `<aio.h>`
* `<wordexp.h>`
- * Thread cancellation (`pthread_cancel`).
+ * Thread cancellation (`pthread_cancel`). Unlikely to ever be implemented
+ because of the difficulty and cost of implementing it, and the difficulty
+ of using it correctly. See
+ [This is why we can't have safe cancellation points](https://lwn.net/Articles/683118/)
+ for more about thread cancellation.
* Robust mutexes
Run `./libc/tools/check-symbols-glibc.py` in bionic/ for the current