62 lines
2.0 KiB
Racket
62 lines
2.0 KiB
Racket
#lang scribble/doc
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@(require "utils.rkt" (for-label ffi/unsafe/atomic))
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@title{Atomic Execution}
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@defmodule[ffi/unsafe/atomic]
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@deftogether[(
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@defproc[(start-atomic) void?]
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@defproc[(end-atomic) void?]
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)]{
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Disables and enables context switches and delivery of break exceptions
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at the level of Racket threads. Calls to @racket[start-atomic] and
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@racket[end-atomic] can be nested.
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Using @racket[call-as-atomic] is somewhat safer, in that
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@racket[call-as-atomic] correctly catches exceptions and re-raises
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them after exiting atomic mode. For simple uses where exceptions need
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not be handled, however, @racket[start-atomic] and @racket[end-atomic]
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are faster.}
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@deftogether[(
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@defproc[(start-breakable-atomic) void?]
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@defproc[(end-breakable-atomic) void?]
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)]{
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Like @racket[start-atomic] and @racket[end-atomic], but the delivery
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of break exceptions is not suspended. To ensure that a call to
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@racket[start-atomic] is reliably paired with a call to
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@racket[end-atomic], use @racket[dynamic-wind] pre- and post thunks or
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some other context where breaks are disabled. These variants are not
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faster than plan @racket[start-atomic] and @racket[end-atomic].}
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@defproc[(call-as-atomic [thunk (-> any)]) any]{
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Calls @racket[thunk] in atomic mode. If @racket[thunk] raises and
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exception, the exception is caught and re-raised after exiting atomic
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mode.
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When @racket[call-as-atomic] is used in the dynamic extent of
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@racket[call-as-atomic], then @racket[thunk] is simply called directly
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(as a non-tail call).}
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@defproc[(call-as-nonatomic [thunk (-> any)]) any]{
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Within the dynamic extent of a @racket[call-as-atomic], calls
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@racket[thunk] in non-atomic mode. Beware that the current thread
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maybe suspended or terminated by other threads during @racket[thunk],
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in which case the call never returns.
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When used not in the dynamic extent of @racket[call-as-atomic],
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@racket[call-as-nonatomic] raises @racket[exn:fail:contract].}
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@defproc[(in-atomic-mode?) boolean?]{
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Returns @racket[#t] if Racket context switches are disables,
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@racket[#f] otherwise.}
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