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attributes.7: Comment out 'fd' text 

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk 2014-10-18 12:54:19 +02:00
parent 06f3aba645
commit 04c95a3bb5
1 changed files with 42 additions and 42 deletions
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@ -725,48 +725,48 @@ running or asynchronous signals are enabled,
and so the data structure can be considered and so the data structure can be considered
effectively constant in these contexts, effectively constant in these contexts,
which makes the former safe. which makes the former safe.
.TP .\" .TP
.I fd .\" .I fd
Functions annotated with .\" Functions annotated with
.I fd .\" .I fd
as an AC-Safety issue may leak file .\" as an AC-Safety issue may leak file
descriptors if asynchronous thread cancellation interrupts their .\" descriptors if asynchronous thread cancellation interrupts their
execution. .\" execution.
.\"
Functions that allocate or deallocate file descriptors will generally be .\" Functions that allocate or deallocate file descriptors will generally be
marked as such. .\" marked as such.
Even if they attempted to protect the file descriptor .\" Even if they attempted to protect the file descriptor
allocation and deallocation with cleanup regions, .\" allocation and deallocation with cleanup regions,
allocating a new descriptor and storing its number where the cleanup region .\" allocating a new descriptor and storing its number where the cleanup region
could release it cannot be performed as a single atomic operation. .\" could release it cannot be performed as a single atomic operation.
Similarly, .\" Similarly,
releasing the descriptor and taking it out of the data structure .\" releasing the descriptor and taking it out of the data structure
normally responsible for releasing it cannot be performed atomically. .\" normally responsible for releasing it cannot be performed atomically.
There will always be a window in which the descriptor cannot be released .\" There will always be a window in which the descriptor cannot be released
because it was not stored in the cleanup handler argument yet, .\" because it was not stored in the cleanup handler argument yet,
or it was already taken out before releasing it. .\" or it was already taken out before releasing it.
It cannot be taken out after release: .\" .\" It cannot be taken out after release:
an open descriptor could mean either that the descriptor still .\" an open descriptor could mean either that the descriptor still
has to be closed, .\" has to be closed,
or that it already did so but the descriptor was .\" or that it already did so but the descriptor was
reallocated by another thread or signal handler. .\" reallocated by another thread or signal handler.
.\"
Such leaks could be internally avoided, with some performance penalty, .\" Such leaks could be internally avoided, with some performance penalty,
by temporarily disabling asynchronous thread cancellation. .\" by temporarily disabling asynchronous thread cancellation.
However, .\" However,
since callers of allocation or deallocation functions would have to do .\" since callers of allocation or deallocation functions would have to do
this themselves, to avoid the same sort of leak in their own layer, .\" this themselves, to avoid the same sort of leak in their own layer,
it makes more sense for the library to assume they are taking care of it .\" it makes more sense for the library to assume they are taking care of it
than to impose a performance penalty that is redundant when the problem .\" than to impose a performance penalty that is redundant when the problem
is solved in upper layers, and insufficient when it is not. .\" is solved in upper layers, and insufficient when it is not.
.\"
This remark by itself does not cause a function to be regarded as .\" This remark by itself does not cause a function to be regarded as
AC-Unsafe. .\" AC-Unsafe.
However, cumulative effects of such leaks may pose a .\" However, cumulative effects of such leaks may pose a
problem for some programs. .\" problem for some programs.
If this is the case, .\" If this is the case,
suspending asynchronous cancellation for the duration of calls .\" suspending asynchronous cancellation for the duration of calls
to such functions is recommended. .\" to such functions is recommended.
.TP .TP
.I mem .I mem
Functions annotated with Functions annotated with