Add explicit safepoints on 1.8.

lib/cudadrv/occupancy.jl

@@ -36,7 +36,13 @@ end
 # HACK: callback function for `launch_configuration` on platforms without support for
 # trampolines as used by `@cfunction` (JuliaLang/julia#27174, JuliaLang/julia#32154)
 _shmem_cb = nothing
-_shmem_cint_cb(x::Cint) = Cint(something(_shmem_cb)(x))
+function _shmem_cint_cb(x::Cint)
+ # see @gcsafe_ccall documentation
+ @static if VERSION < v"1.9"
+ GC.safepoint()
+ end
+ Cint(something(_shmem_cb)(x))
+end
 _shmem_cb_lock = Threads.ReentrantLock()
 
 """
@@ -58,7 +64,13 @@ function launch_configuration(fun::CuFunction; shmem::Union{Integer,Base.Callabl
  if isa(shmem, Integer)
  cuOccupancyMaxPotentialBlockSize(blocks_ref, threads_ref, fun, C_NULL, shmem, max_threads)
  elseif Sys.ARCH == :x86 || Sys.ARCH == :x86_64
- shmem_cint = threads -> Cint(shmem(threads))
+ function shmem_cint(threads)
+ # see @gcsafe_ccall documentation
+ @static if VERSION < v"1.9"
+ GC.safepoint()
+ end
+ Cint(shmem(threads))
+ end
  cb = @cfunction($shmem_cint, Cint, (Cint,))
  cuOccupancyMaxPotentialBlockSize(blocks_ref, threads_ref, fun, cb, 0, max_threads)
  else

lib/utils/call.jl

@@ -165,6 +165,12 @@ render_arg(io, arg::Union{<:Base.RefValue, AbstractArray}) = summary(io, arg)
 
 # TODO: replace with JuliaLang/julia#49933 once merged
 
+# note that this is generally only safe with functions that do not call back into Julia.
+# when callbacks occur, the code should ensure the GC is not running:
+# - on 1.10 and later, everything is fine because of safepoint_on_entry
+# - on 1.9, @cfunction-based callbacks are fine because they transition to gc_unsafe
+# - on 1.8 and earlier, the code should explicitly call GC.safepoint()!
+
 function ccall_macro_lower(func, rettype, types, args, nreq)
  # instead of re-using ccall or Expr(:foreigncall) to perform argument conversion,
  # we need to do so ourselves in order to insert a jl_gc_safe_enter|leave