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avoid startup deadlock in scheduler #59583

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Merged
merged 1 commit into from
Sep 24, 2025
Merged

avoid startup deadlock in scheduler #59583

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14 changes: 10 additions & 4 deletions base/lock.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -797,7 +797,7 @@ end


# share a lock/condition, since we just need it briefly, so some contention is okay
const PerThreadLock = ThreadSynchronizer()
const PerThreadLock = Threads.SpinLock()
"""
OncePerThread{T}(init::Function)() -> T

Expand Down Expand Up @@ -901,7 +901,15 @@ OncePerThread(initializer) = OncePerThread{Base.promote_op(initializer), typeof(
state = @atomic :monotonic ss[tid]
while state == PerStateConcurrent
# lost race, wait for notification this is done running elsewhere
wait(PerThreadLock) # wait for initializer to finish without releasing this thread
# without releasing this thread
unlock(PerThreadLock)
while state == PerStateConcurrent
# spin loop until ready
ss = @atomic :acquire once.ss
state = @atomic :monotonic ss[tid]
GC.safepoint()
end
lock(PerThreadLock)
ss = @atomic :monotonic once.ss
state = @atomic :monotonic ss[tid]
end
Expand All @@ -915,7 +923,6 @@ OncePerThread(initializer) = OncePerThread{Base.promote_op(initializer), typeof(
lock(PerThreadLock)
ss = @atomic :monotonic once.ss
@atomic :release ss[tid] = PerStateErrored
notify(PerThreadLock)
rethrow()
end
# store result and notify waiters
Expand All @@ -924,7 +931,6 @@ OncePerThread(initializer) = OncePerThread{Base.promote_op(initializer), typeof(
@atomic :release xs[tid] = result
ss = @atomic :monotonic once.ss
@atomic :release ss[tid] = PerStateHasrun
notify(PerThreadLock)
elseif state == PerStateErrored
error("OncePerThread initializer failed previously")
elseif state != PerStateHasrun
Expand Down