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net: create resolver semaphore channels eagerly - #80906

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net: create resolver semaphore channels eagerly#80906
serhiy-bzhezytskyy wants to merge 1 commit into
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serhiy-bzhezytskyy:net-eager-sema-channels

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@serhiy-bzhezytskyy serhiy-bzhezytskyy commented Aug 16, 2026

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A lookup from outside a testing/synctest bubble, after net's resolver has been used inside one, aborts with "send on synctest channel from outside bubble". One test order runs to completion and another aborts the process, and a fatal error reports no failing test.

resolverConfig.ch and nsswitchConfig.ch are created inside their initOnce.Do, so each is associated with the bubble of the first caller to reach the resolver.

Both are used only as one-slot semaphores, so they are now created in their package-level var initializers, where no bubble exists. That removes the ordering dependence at no cost.

threadLimit in net.go has the same shape but is left alone: its capacity derives from rlim.Cur, and a program may lower RLIMIT_NOFILE after package initialization, so eager creation could permit more concurrent getaddrinfo calls than there are descriptors.

Updates #80903

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A lookup from outside a testing/synctest bubble, after net's resolver
has been used inside one, aborts with "send on synctest channel from
outside bubble". One test order runs to completion and another aborts
the process, and a fatal error reports no failing test.

resolverConfig.ch and nsswitchConfig.ch are created inside their
initOnce.Do, so each is associated with the bubble of the first caller
to reach the resolver.

Both are used only as one-slot semaphores, so they are now created in
their package-level var initializers, where no bubble exists. That
removes the ordering dependence at no cost.

threadLimit in net.go has the same shape but is left alone: its
capacity derives from rlim.Cur, and a program may lower RLIMIT_NOFILE
after package initialization, so eager creation could permit more
concurrent getaddrinfo calls than there are descriptors.

Updates golang#80903
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