Skip to content

fix crashes using multithreaded julia from python #758

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
dpinol wants to merge 2 commits into
base: main
Choose a base branch
from
+22 −4
Open

fix crashes using multithreaded julia from python #758

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
b25076b
fix: rare crash due to race condition
Apr 12, 2026
7d79ab5
fix: no GC disable. avoid resize PYJLFREEVALUES in dealloc
May 27, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 22 additions & 4 deletions src/JlWrap/C.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,14 @@ const PyJuliaBase_Type = Ref(C.PyNULL)
# we store the actual julia values here
# the `value` field of `PyJuliaValueObject` indexes into here
const PYJLVALUES = []
# unused indices in PYJLVALUES
# unused indices in PYJLVALUES; kept the same length as PYJLVALUES (extra slots
# are pushed alongside PYJLVALUES so the dealloc/finalizer path never has to
# resize this vector). Only the first PYJLFREEVALUECOUNT[] entries are valid
# free indices; the rest are placeholders.
const PYJLFREEVALUES = Int[]
const PYJLFREEVALUECOUNT = Ref(0)
# lock protecting PYJLVALUES, PYJLFREEVALUES and PYJLFREEVALUECOUNT
const PYJL_LOCK = Threads.SpinLock()

function _pyjl_new(t::C.PyPtr, ::C.PyPtr, ::C.PyPtr)
alloc = C.PyType_GetSlot(t, C.Py_tp_alloc)
Expand All @@ -39,8 +45,14 @@ end
function _pyjl_dealloc(o::C.PyPtr)
idx = C.@ft UnsafePtr{PyJuliaValueObject}(o).value[]
if idx != 0
# No allocation in this critical section: PYJLFREEVALUES has been pre-sized
# to match PYJLVALUES by PyJuliaValue_SetValue, so recording a free index is
# just a write to an existing slot plus a counter bump. This avoids the GC-triggered
lock(PYJL_LOCK)
PYJLVALUES[idx] = nothing
push!(PYJLFREEVALUES, idx)
PYJLFREEVALUECOUNT[] += 1
PYJLFREEVALUES[PYJLFREEVALUECOUNT[]] = idx
unlock(PYJL_LOCK)
end
(C.@ft UnsafePtr{PyJuliaValueObject}(o).weaklist[!]) == C.PyNULL || C.PyObject_ClearWeakRefs(o)
freeptr = C.PyType_GetSlot(C.Py_Type(o), C.Py_tp_free)
Expand Down Expand Up @@ -375,13 +387,19 @@ PyJuliaValue_SetValue(_o, @nospecialize(v)) = Base.GC.@preserve _o begin
o = C.asptr(_o)
idx = C.@ft UnsafePtr{PyJuliaValueObject}(o).value[]
if idx == 0
if isempty(PYJLFREEVALUES)
lock(PYJL_LOCK)
if PYJLFREEVALUECOUNT[] == 0
# Grow both vectors together so length(PYJLFREEVALUES) == length(PYJLVALUES)
# is preserved. The 0 in PYJLFREEVALUES is just a placeholder
push!(PYJLVALUES, v)
push!(PYJLFREEVALUES, 0)
idx = length(PYJLVALUES)
else
idx = pop!(PYJLFREEVALUES)
idx = PYJLFREEVALUES[PYJLFREEVALUECOUNT[]]
PYJLFREEVALUECOUNT[] -= 1
PYJLVALUES[idx] = v
end
unlock(PYJL_LOCK)
C.@ft UnsafePtr{PyJuliaValueObject}(o).value[] = idx
else
PYJLVALUES[idx] = v
Expand Down
Loading