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pcre: remove nthreads constant dependency #44542

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Merged
merged 3 commits into from
Mar 15, 2022
Merged

pcre: remove nthreads constant dependency #44542

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85c8b6d
pcre: remove nthreads constant dependency
vtjnash Mar 10, 2022
f62ac47
Merge branch 'master' into jn/axe-resize_nthreads
DilumAluthge Mar 13, 2022
555afab
Merge branch 'master' into jn/axe-resize_nthreads
DilumAluthge Mar 14, 2022
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4 changes: 4 additions & 0 deletions base/Base.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -504,6 +504,10 @@ function __init__()
nothing
end

# enable threads support
@eval PCRE PCRE_COMPILE_LOCK = Threads.SpinLock()

end


end # baremodule Base
4 changes: 0 additions & 4 deletions base/client.jl
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Expand Up @@ -514,10 +514,6 @@ MainInclude.include
function _start()
empty!(ARGS)
append!(ARGS, Core.ARGS)
if ccall(:jl_generating_output, Cint, ()) != 0 && JLOptions().incremental == 0
# clear old invalid pointers
PCRE.__init__()
end
try
exec_options(JLOptions())
catch
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39 changes: 29 additions & 10 deletions base/pcre.jl
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Expand Up @@ -24,28 +24,47 @@ function create_match_context()
return ctx
end

const THREAD_MATCH_CONTEXTS = Ptr{Cvoid}[C_NULL]
THREAD_MATCH_CONTEXTS::Vector{Ptr{Cvoid}} = [C_NULL]

PCRE_COMPILE_LOCK = nothing

_tid() = Int(ccall(:jl_threadid, Int16, ())+1)
_tid() = Int(ccall(:jl_threadid, Int16, ())) + 1
_nth() = Int(unsafe_load(cglobal(:jl_n_threads, Cint)))

function get_local_match_context()
global THREAD_MATCH_CONTEXTS
tid = _tid()
ctx = @inbounds THREAD_MATCH_CONTEXTS[tid]
ctxs = THREAD_MATCH_CONTEXTS
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I find it scary that we rely on "implicit" atomic ordering of global for code like this. It looks so innocent and the nuance can get lost during refactoring (even though I understand it is unlikely to happen for this part of code). Rather, I think it'd be easier to encode the atomic ordering by doing something like const THREAD_MATCH_CONTEXTS = Threads.Atomic(Ptr{Cvoid}[C_NULL]).

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Yeah, I am just waiting on #44231 to be able to specify it explicitly. For now, I am okay with relying on the specified behavior implicitly.

if length(ctxs) < tid
# slow path to allocate it
l = PCRE_COMPILE_LOCK::Threads.SpinLock
lock(l)
try
THREAD_MATCH_CONTEXTS = ctxs = copyto!(fill(C_NULL, _nth()), THREAD_MATCH_CONTEXTS)
finally
unlock(l)
end
end
ctx = @inbounds ctxs[tid]
if ctx == C_NULL
@inbounds THREAD_MATCH_CONTEXTS[tid] = ctx = create_match_context()
# slow path to allocate it
ctx = create_match_context()
l = PCRE_COMPILE_LOCK
if l === nothing
THREAD_MATCH_CONTEXTS[tid] = ctx
else
l = l::Threads.SpinLock
lock(l)
try
THREAD_MATCH_CONTEXTS[tid] = ctx
finally
unlock(l)
end
end
end
return ctx
end

function __init__()
resize!(THREAD_MATCH_CONTEXTS, _nth())
fill!(THREAD_MATCH_CONTEXTS, C_NULL)
global PCRE_COMPILE_LOCK = Threads.SpinLock()
end

# supported options for different use cases

# arguments to pcre2_compile
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