Make threadcall gc safe #55956
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Make threadcall gc safe #55956
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gbaraldi
added
backport 1.10
vchuravy
reviewed
Oct 1, 2024
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Someone should finish #49933 |
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Just to confirm, is it safe to call |
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"GC safepoint" are singular points in time. GC safe regions are spans in time, and yes it is legal to to nest safe regions. |
vchuravy
reviewed
Oct 1, 2024
base/threadcall.jl
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| @@ -43,7 +43,9 @@ macro threadcall(f, rettype, argtypes, argvals...) | |||
| push!(body, :(p += Core.sizeof($T))) | |||
| push!(args, arg) | |||
| end | |||
| push!(body, :(gc_state = ccall(:jl_gc_safe_enter, Int8, (), ))) | |||
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So a problem with this is that the ccall lowering will insert calls to cconvert and then unsafe_convert. cconvert is designed to allocate.
So you manually need to insert the code to lower include aGC.@preserve
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Have I told you how much I dislike threadcall?
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Also see JuliaInterop/ObjectiveC.jl@2578dc2, which is even more relevant (it turns a ccall into a GC-safe ccall after manually doing argument conversion first). It would almost be easier to fix #49933 at this point...
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The issue is that we need to backport this :(
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vchuravy
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Oct 16, 2024
| @@ -39,13 +39,19 @@ macro threadcall(f, rettype, argtypes, argvals...) | |||
| args = Symbol[] | |||
| for (i, T) in enumerate(argtypes) | |||
| arg = Symbol("arg", i) | |||
| push!(body, :($arg = unsafe_load(convert(Ptr{$T}, p)))) | |||
| push!(body, :($arg = unsafe_convert($T, cconvert($T, unsafe_load(convert(Ptr{$T}, p)))))) | |||
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I don't fully understand the code here (why is there an unsafe_load), but the return from cconvert must be GC preserved.
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Threadcall passes the args in an array of ptrs if I understood the code correctly
| push!(body, :(unsafe_store!(convert(Ptr{$rettype}, retval_ptr), ret))) | ||
| push!(body, :(return Int(Core.sizeof($rettype)))) | ||
| append!(body, (quote | ||
| GC.@preserve $(args...) begin |
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You are preserving the unsafe_convert not the cconvert here, right?
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DilumAluthge
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Sep 5, 2025
Backported PRs: - [x] #54840 <!-- Add boundscheck in speccache_eq to avoid OOB access due to data race --> - [x] #42080 <!-- recommend explicit `using Foo: Foo, ...` in package code (was: "using considered harmful") --> - [x] #58127 <!-- [DOC] Update installation docs: /downloads/ => /install/ --> - [x] #58202 <!-- [release-1.11] malloc: use jl_get_current_task to fix null check --> - [x] #58584 <!-- Make `Ptr` values static-show w/ type-information --> - [x] #58637 <!-- Make late gc lower handle insertelement of alloca use. --> - [x] #58837 <!-- fix null comparisons for non-standard address spaces --> - [x] #57826 <!-- Add a `similar` method for `Type{<:CodeUnits}` --> - [x] #58293 <!-- fix trailing indices stackoverflow in reinterpreted array --> - [x] #58887 <!-- Pkg: Allow configuring can_fancyprint(io::IO) using IOContext --> - [x] #58937 <!-- Fix nthreadpools size in JLOptions --> - [x] #58978 <!-- Fix precompilepkgs warn loaded setting --> - [x] #58998 <!-- Bugfix: Use Base.aligned_sizeof instead of sizeof in Mmap.mmap --> - [x] #59120 <!-- Fix memory order typo in "src/julia_atomics.h" --> - [x] #59170 <!-- Clarify and enhance confusing precompile test --> Need manual backport: - [ ] #56329 <!-- loading: clean up more concurrency issues --> - [ ] #56956 <!-- Add "mea culpa" to foreign module assignment error. --> - [ ] #57035 <!-- linux: workaround to avoid deadlock inside dl_iterate_phdr in glibc --> - [ ] #57089 <!-- Block thread from receiving profile signal with stackwalk lock --> - [ ] #57249 <!-- restore non-freebsd-unix fix for profiling --> - [ ] #58011 <!-- Remove try-finally scope from `@time_imports` `@trace_compile` `@trace_dispatch` --> - [ ] #58062 <!-- remove unnecessary edge from `exp_impl` to `pow` --> - [ ] #58157 <!-- add showing a string to REPL precompile workload --> - [ ] #58209 <!-- Specialize `one` for the `SizedArray` test helper --> - [ ] #58108 <!-- Base.get_extension & Dates.format made public --> - [ ] #58356 <!-- codegen: remove readonly from abstract type calling convention --> - [ ] #58415 <!-- [REPL] more reliable extension loading --> - [ ] #58510 <!-- Don't filter `Core` methods from newly-inferred list --> - [ ] #58110 <!-- relax dispatch for the `IteratorSize` method for `Generator` --> - [ ] #58965 <!-- Fix `hygienic-scope`s in inner macro expansions --> - [ ] #58971 <!-- Fix alignment of failed precompile jobs on CI --> - [ ] #59066 <!-- build: Also pass -fno-strict-aliasing for C++ --> Contains multiple commits, manual intervention needed: - [ ] #55877 <!-- fix FileWatching designs and add workaround for a stat bug on Apple --> - [ ] #56755 <!-- docs: fix scope type of a `struct` to hard --> - [ ] #57809 <!-- Fix fptrunc Float64 -> Float16 rounding through Float32 --> - [ ] #57398 <!-- Make remaining float intrinsics require float arguments --> - [ ] #56351 <!-- Fix `--project=@script` when outside script directory --> - [ ] #57129 <!-- clarify that time_ns is monotonic --> - [ ] #58134 <!-- Note annotated string API is experimental in Julia 1.11 in HISTORY.md --> - [ ] #58401 <!-- check that hashing of types does not foreigncall (`jl_type_hash` is concrete evaluated) --> - [ ] #58435 <!-- Fix layout flags for types that have oddly sized primitive type fields --> - [ ] #58483 <!-- Fix tbaa usage when storing into heap allocated immutable structs --> - [ ] #58512 <!-- Make more types jl_static_show readably --> - [ ] #58012 <!-- Re-enable tab completion of kwargs for large method tables --> - [ ] #58683 <!-- Add 0 predecessor to entry basic block and handle it in inlining --> - [ ] #59112 <!-- Add builtin function name to add methods error --> Non-merged PRs with backport label: - [ ] #59329 <!-- aotcompile: destroy LLVM context after serializing combined module --> - [ ] #58848 <!-- Set array size only when safe to do so --> - [ ] #58535 <!-- gf.c: include const-return methods in `--trace-compile` --> - [ ] #58038 <!-- strings/cstring: `transcode`: prevent Windows sysimage invalidation --> - [ ] #57604 <!-- `@nospecialize` for `string_index_err` --> - [ ] #57366 <!-- Use ptrdiff_t sized offsets for gvars_offsets to allow large sysimages --> - [ ] #56890 <!-- Enable getting non-boxed LLVM type from Julia Type --> - [ ] #56823 <!-- Make version of opaque closure constructor in world --> - [ ] #55958 <!-- also redirect JL_STDERR etc. when redirecting to devnull --> - [ ] #55956 <!-- Make threadcall gc safe --> - [ ] #55534 <!-- Set stdlib sources as read-only during installation --> - [ ] #55499 <!-- propagate the terminal's `displaysize` to the `IOContext` used by the REPL --> - [ ] #55458 <!-- Allow for generically extracting unannotated string --> - [ ] #55457 <!-- Make AnnotateChar equality consider annotations --> - [ ] #55220 <!-- `isfile_casesensitive` fixes on Windows --> - [ ] #53957 <!-- tweak how filtering is done for what packages should be precompiled --> - [ ] #51479 <!-- prevent code loading from lookin in the versioned environment when building Julia --> - [ ] #50813 <!-- More doctests for Sockets and capitalization fix --> - [ ] #50157 <!-- improve docs for `@inbounds` and `Base.@propagate_inbounds` --> --------- Co-authored-by: Kiran Pamnany <[email protected]> Co-authored-by: adienes <[email protected]> Co-authored-by: Gabriel Baraldi <[email protected]> Co-authored-by: Keno Fischer <[email protected]> Co-authored-by: Simeon David Schaub <[email protected]> Co-authored-by: Jameson Nash <[email protected]> Co-authored-by: Alex Arslan <[email protected]> Co-authored-by: Fons van der Plas <[email protected]> Co-authored-by: Ian Butterworth <[email protected]> Co-authored-by: JonasIsensee <[email protected]> Co-authored-by: Curtis Vogt <[email protected]> Co-authored-by: Dilum Aluthge <[email protected]> Co-authored-by: DilumAluthgeBot <[email protected]> Co-authored-by: DilumAluthge <[email protected]>
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threadcall cannot call julia code. But due to thread adoption it currently is not marked gc safe. Which means that a blocking call will cause a hang in the GC