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Message-ID: <20130508085431.GC12689@port70.net>
Date: Wed, 8 May 2013 10:54:31 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: Proposed new cancellation type
* Rich Felker <dalias@...ifal.cx> [2013-05-07 20:57:29 -0400]:
>
> 1. With normal cancellation, when the cancellation request is acted
> on, cancellation is disabled, so that further calls to cancellation
> points in the cleanup handlers don't in turn get cancelled. Would
> it make sense for only the _first_ cancellation point called to
> fail with ECANCELED (and after that, for cancellation to remain
> disabled)? Or should all fail until it's explicitly disabled?
>
i think libraries should be prepared for this
ECANCELLED either way
- first only strategy:
eg in fflush(0) several blocking syscalls
are made in a loop, it should return when
ECANCELLED is detected to avoid further
blocking
another issue is that the failure of some
cancellation points are not reported by
libraries: eg close is a cancellation point
but its failure is usually not treated as
an error so cancellation can be unnoticed
- cancel everything strategy:
libraries that try to act on errors
(eg log some error message) will
fail to do so, which can be bad if the
cleanup code of the library requires
blocking calls
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