Add a safepoint in the maybe_destroy_plan spin lock (#205)

* Add a safepoint in the maybe_destroy_plan spin lock

* Fix typo

Author: Octogonapus

Project.toml

@@ -1,6 +1,6 @@
 name = "FFTW"
 uuid = "7a1cc6ca-52ef-59f5-83cd-3a7055c09341"
-version = "1.4.1"
+version = "1.4.2"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"

src/fft.jl

@@ -304,7 +304,11 @@ function maybe_destroy_plan(plan::FFTWPlan)
     # since task switches aren't permitted in finalizers.   This has suboptimal efficiency,
     # but we shouldn't waste too many cycles since destroying plans is quick and contention
     # should be rare.
-    while !trylock(deferred_destroy_lock); end
+    while !trylock(deferred_destroy_lock)
+        # Need a safepoint in here because without it, this loop blocks forward progress in the GC and can deadlock
+        # the program.
+        GC.safepoint()
+    end
     try
         # note: fftwlock is re-entrant, so trylock will succeed here if we
         # are in the task that holds the planner lock.  That's okay —