Gidday Michael,
Asynchronous cancelability
means that the thread can be canceled at any time
(usually immediately, but the system does not guarantee this).
Deferred cancelability means that cancellation will be delayed until
the thread next calls a function that is a
.IR "cancellation point" .
A list of functions that are or may be cancellation points is
provided in
.IR pthreads (7).
It is very important to document the list of functions that are/are
not CP in the "may be a CP" list: this is system specific and belongs
to the system documentation.
For man-pages-3.14, I have added POSIX.1's lists of "are" and "may be"
cancellation points to pthreads.7.
However, it unclear to me how one determines the list of functions
that are cancellation points under glibc. Do you have some ideas
about this?
I checked out, and I found no obvious to extract the information
automatically from the source. We may have to ask support from the Glibc
folks.
.SH NOTES
On Linux, cancellation is implemented using signals.
Under the NPTL threading implementation,
the first real-time signal (i.e., signal 32) is used for this purpose.
Hmmm... You are right: NPTL uses the first real-time signal (32)
provided by the *kernel*. As a matter of fact, Glibc reserves kernel
real-time signals 32 and 33 for NPTL; real-time queued signals
available to the application ranges from SIGRTMIN (34) to SIGRTMAX(64).
Yes... exactly.
On LinuxThreads, the second real-time signal is used,
if real-time signals are available, otherwise
.B SIGUSR2
is used.
IIRC, this was true on 'older LinuxThreads'. Never used real-time
queued signals as well ? (To verify...)
I'm not quite sure what you want to say there. Can you say some
more please.
Sorry, typo and missing words make this sentence hard to understand...
Second try:
Newer version of LinuxThreads uses RT signal as well? (this claim has to
be verified).
.SH EXAMPLE
[...]
sleep(3) is a CP on Linux (AFAIR, sleep is a "may be CP").
Not sure what you are wanting to saying here; should something
be changed in the page? (BTW: sleep() *is* a CP in POSIX.1.)
[...]
I hadn't the list at hand, and I thought mistakenly that sleep() is not
a mandatory CP. Thanks for the note.
Cheers,
Loïc.
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