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Run FFTW in GC-safe regions #340

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63 changes: 43 additions & 20 deletions src/fft.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,11 @@ function get_num_threads()
end
end

# Whether a plan created now with the current planner settings will re-enter
# Julia through the `spawnloop` threading callback when executed. Only needed
# with FFTW since MKL handles its own threading.
_plan_is_threaded() = fftw_provider == "fftw" && get_num_threads() > 1

@exclusive function set_num_threads(f::Function, num_threads::Integer)
orig_num_threads = get_num_threads()
_set_num_threads(num_threads)
Expand Down Expand Up @@ -261,11 +266,12 @@ for P in (:cFFTWPlan, :rFFTWPlan) # complex, r2c/c2r
oalign::Int32 # alignment mod 16 of input
flags::UInt32 # planner flags
region::G # region (iterable) of dims that are transformed
threaded::Bool # whether execution re-enters Julia via the spawnloop callback
pinv::ScaledPlan
function $P{T,K,inplace,N,G}(plan::PlanPtr, flags::Integer, R::G,
X::StridedArray{T,N}, Y::StridedArray) where {T<:fftwNumber,K,inplace,N,G}
p = new(plan, size(X), size(Y), strides(X), strides(Y),
alignment_of(X), alignment_of(Y), flags, R)
alignment_of(X), alignment_of(Y), flags, R, _plan_is_threaded())
finalizer(maybe_destroy_plan, p)
p
end
Expand All @@ -290,12 +296,13 @@ mutable struct r2rFFTWPlan{T<:fftwNumber,K,inplace,N,G} <: FFTWPlan{T,K,inplace}
flags::UInt32 # planner flags
region::G # region (iterable) of dims that are transformed
kinds::K
threaded::Bool # whether execution re-enters Julia via the spawnloop callback
pinv::ScaledPlan
function r2rFFTWPlan{T,K,inplace,N,G}(plan::PlanPtr, flags::Integer, R::G,
X::StridedArray{T,N},
Y::StridedArray, kinds::K) where {T<:fftwNumber,K,inplace,N,G}
p = new(plan, size(X), size(Y), strides(X), strides(Y),
alignment_of(X), alignment_of(Y), flags, R, kinds)
alignment_of(X), alignment_of(Y), flags, R, kinds, _plan_is_threaded())
finalizer(maybe_destroy_plan, p)
p
end
Expand Down Expand Up @@ -511,51 +518,67 @@ _colmajorstrides(p) = ()

# Execute

macro execute(plan, ccallexpr)
quote
if $(esc(plan)).threaded
# If the plan is multi-threaded then we execute it directly. It will
# end up calling spawnloop(), which will enter a GC-safe region.
$(esc(ccallexpr))
else
# If the plan is single-threaded then it won't call back into Julia
# and we can execute it in a GC-safe region.
gc_state = @ccall jl_gc_safe_enter()::Int8
$(esc(ccallexpr))
@ccall jl_gc_safe_leave(gc_state::Int8)::Cvoid
end
end
end

unsafe_execute!(plan::FFTWPlan{<:fftwDouble}) =
ccall((:fftw_execute,libfftw3), Cvoid, (PlanPtr,), plan)
@execute plan ccall((:fftw_execute,libfftw3), Cvoid, (PlanPtr,), plan)

unsafe_execute!(plan::FFTWPlan{<:fftwSingle}) =
ccall((:fftwf_execute,libfftw3f), Cvoid, (PlanPtr,), plan)
@execute plan ccall((:fftwf_execute,libfftw3f), Cvoid, (PlanPtr,), plan)

unsafe_execute!(plan::cFFTWPlan{T},
X::StridedArray{T}, Y::StridedArray{T}) where {T<:fftwDouble} =
ccall((:fftw_execute_dft,libfftw3), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)
@execute plan ccall((:fftw_execute_dft,libfftw3), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)

unsafe_execute!(plan::cFFTWPlan{T},
X::StridedArray{T}, Y::StridedArray{T}) where {T<:fftwSingle} =
ccall((:fftwf_execute_dft,libfftw3f), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)
@execute plan ccall((:fftwf_execute_dft,libfftw3f), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)

unsafe_execute!(plan::rFFTWPlan{Float64,FORWARD},
X::StridedArray{Float64}, Y::StridedArray{Complex{Float64}}) =
ccall((:fftw_execute_dft_r2c,libfftw3), Cvoid,
(PlanPtr,Ptr{Float64},Ptr{Complex{Float64}}), plan, X, Y)
@execute plan ccall((:fftw_execute_dft_r2c,libfftw3), Cvoid,
(PlanPtr,Ptr{Float64},Ptr{Complex{Float64}}), plan, X, Y)

unsafe_execute!(plan::rFFTWPlan{Float32,FORWARD},
X::StridedArray{Float32}, Y::StridedArray{Complex{Float32}}) =
ccall((:fftwf_execute_dft_r2c,libfftw3f), Cvoid,
(PlanPtr,Ptr{Float32},Ptr{Complex{Float32}}), plan, X, Y)
@execute plan ccall((:fftwf_execute_dft_r2c,libfftw3f), Cvoid,
(PlanPtr,Ptr{Float32},Ptr{Complex{Float32}}), plan, X, Y)

unsafe_execute!(plan::rFFTWPlan{Complex{Float64},BACKWARD},
X::StridedArray{Complex{Float64}}, Y::StridedArray{Float64}) =
ccall((:fftw_execute_dft_c2r,libfftw3), Cvoid,
(PlanPtr,Ptr{Complex{Float64}},Ptr{Float64}), plan, X, Y)
@execute plan ccall((:fftw_execute_dft_c2r,libfftw3), Cvoid,
(PlanPtr,Ptr{Complex{Float64}},Ptr{Float64}), plan, X, Y)

unsafe_execute!(plan::rFFTWPlan{Complex{Float32},BACKWARD},
X::StridedArray{Complex{Float32}}, Y::StridedArray{Float32}) =
ccall((:fftwf_execute_dft_c2r,libfftw3f), Cvoid,
(PlanPtr,Ptr{Complex{Float32}},Ptr{Float32}), plan, X, Y)
@execute plan ccall((:fftwf_execute_dft_c2r,libfftw3f), Cvoid,
(PlanPtr,Ptr{Complex{Float32}},Ptr{Float32}), plan, X, Y)

unsafe_execute!(plan::r2rFFTWPlan{T},
X::StridedArray{T}, Y::StridedArray{T}) where {T<:fftwDouble} =
ccall((:fftw_execute_r2r,libfftw3), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)
@execute plan ccall((:fftw_execute_r2r,libfftw3), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)

unsafe_execute!(plan::r2rFFTWPlan{T},
X::StridedArray{T}, Y::StridedArray{T}) where {T<:fftwSingle} =
ccall((:fftwf_execute_r2r,libfftw3f), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)
@execute plan ccall((:fftwf_execute_r2r,libfftw3f), Cvoid,
(PlanPtr,Ptr{T},Ptr{T}), plan, X, Y)

# NOTE ON GC (garbage collection):
# The FFTWPlan has a finalizer so that gc will destroy the plan,
Expand Down
8 changes: 7 additions & 1 deletion src/providers.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,13 @@ end
# tasks (FFTW/fftw3#175):
function spawnloop(f::Ptr{Cvoid}, fdata::Ptr{Cvoid}, elsize::Csize_t, num::Cint, callback_data::Ptr{Cvoid})
@sync for i = 0:num-1
Threads.@spawn ccall(f, Ptr{Cvoid}, (Ptr{Cvoid},), fdata + elsize*i)
Threads.@spawn begin
# Run the FFTW work chunk in a GC-safe region so the garbage
# collector can make progress while this thread is blocked.
gc_state = @ccall jl_gc_safe_enter()::Int8
ccall(f, Ptr{Cvoid}, (Ptr{Cvoid},), fdata + elsize*i)
@ccall jl_gc_safe_leave(gc_state::Int8)::Cvoid
end
end
end

Expand Down
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