Revert "Profile: multithread getdict! (redo of JuliaLang#43805) (Juli…

…aLang#43816)"

This reverts commit e6fa3ec.

stdlib/Profile/src/Profile.jl

@@ -401,34 +401,19 @@ function getdict(data::Vector{UInt})
 end
 
 function getdict!(dict::LineInfoDict, data::Vector{UInt})
-    # we don't want metadata here as we're just looking up ips
-    unique_ips = unique(has_meta(data) ? strip_meta(data) : data)
-    n_unique_ips = length(unique_ips)
-    n_unique_ips == 0 && return dict
-    iplookups = similar(unique_ips, Vector{StackFrame})
-    @sync for indexes_part in Iterators.partition(eachindex(unique_ips), div(n_unique_ips, Threads.nthreads(), RoundUp))
-        Threads.@spawn begin
-            for i in indexes_part
-                iplookups[i] = _lookup_corrected(unique_ips[i])
-            end
-        end
-    end
-    for i in eachindex(unique_ips)
-        dict[unique_ips[i]] = iplookups[i]
+    for ip in data
+        # Lookup is expensive, so do it only once per ip.
+        haskey(dict, UInt64(ip)) && continue
+        st = lookup(convert(Ptr{Cvoid}, ip))
+        # To correct line numbers for moving code, put it in the form expected by
+        # Base.update_stackframes_callback[]
+        stn = map(x->(x, 1), st)
+        try Base.invokelatest(Base.update_stackframes_callback[], stn) catch end
+        dict[UInt64(ip)] = map(first, stn)
     end
     return dict
 end
 
-function _lookup_corrected(ip::UInt)
-    st = lookup(convert(Ptr{Cvoid}, ip))
-    # To correct line numbers for moving code, put it in the form expected by
-    # Base.update_stackframes_callback[]
-    stn = map(x->(x, 1), st)
-    # Note: Base.update_stackframes_callback[] should be data-race free
-    try Base.invokelatest(Base.update_stackframes_callback[], stn) catch end
-    return map(first, stn)
-end
-
 """
     flatten(btdata::Vector, lidict::LineInfoDict) -> (newdata::Vector{UInt64}, newdict::LineInfoFlatDict)