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Add better documentation on how id_function() should be defined and what

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issues there are.

PR: 1096
This commit is contained in:
Richard Levitte 2005-06-18 05:52:20 +00:00
parent 77bc62c3a7
commit 140e5c3f3b
1 changed files with 20 additions and 3 deletions
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23
doc/crypto/threads.pod
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@ -65,9 +65,10 @@ B<CRYPTO_LOCK>, and releases it otherwise.
B<file> and B<line> are the file number of the function setting the
lock. They can be useful for debugging.
id_function(void) is a function that returns a thread ID. It is not
id_function(void) is a function that returns a thread ID, for example
pthread_self() if it returns an integer (see NOTES below). It isn't
needed on Windows nor on platforms where getpid() returns a different
ID for each thread (most notably Linux).
ID for each thread (see NOTES below).
Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
of OpenSSL need it for better performance. To enable this, the following
@ -124,7 +125,7 @@ CRYPTO_get_new_dynlockid() returns the index to the newly created lock.
The other functions return no values.
=head1 NOTE
=head1 NOTES
You can find out if OpenSSL was configured with thread support:
@ -139,6 +140,22 @@ You can find out if OpenSSL was configured with thread support:
Also, dynamic locks are currently not used internally by OpenSSL, but
may do so in the future.
Defining id_function(void) has it's own issues. Generally speaking,
pthread_self() should be used, even on platforms where getpid() gives
different answers in each thread, since that may depend on the machine
the program is run on, not the machine where the program is being
compiled. For instance, Red Hat 8 Linux and earlier used
LinuxThreads, whose getpid() returns a different value for each
thread. Red Hat 9 Linux and later use NPTL, which is
Posix-conformant, and has a getpid() that returns the same value for
all threads in a process. A program compiled on Red Hat 8 and run on
Red Hat 9 will therefore see getpid() returning the same value for
all threads.
There is still the issue of platforms where pthread_self() returns
something other than an integer. This is a bit unusual, and this
manual has no cookbook solution for that case.
=head1 EXAMPLES
B<crypto/threads/mttest.c> shows examples of the callback functions on