diff options
author | Richard Levitte <levitte@openssl.org> | 2005-06-18 05:52:16 +0000 |
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committer | Richard Levitte <levitte@openssl.org> | 2005-06-18 05:52:16 +0000 |
commit | eef468e330deeed5ac17cb84e944b9f5b7a75347 (patch) | |
tree | 5738eea8e54c5f44afd45264b137847f0b258ceb | |
parent | 4bd46774bb73bce491e5556f8e43a5d9d8ba4539 (diff) |
Add better documentation on how id_function() should be defined and what
issues there are.
PR: 1096
-rw-r--r-- | doc/crypto/threads.pod | 34 |
1 files changed, 21 insertions, 13 deletions
diff --git a/doc/crypto/threads.pod b/doc/crypto/threads.pod index 98373a9ca8..3df4ecd776 100644 --- a/doc/crypto/threads.pod +++ b/doc/crypto/threads.pod @@ -65,18 +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, for -instance, pthread_self(). It is not, needed on Windows nor on -platforms where getpid() returns a different ID for each thread. -However, even on those platforms, pthread_self() should be used, since -the behavior of getpid() may depend on the machine where the program -is being run, 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 thus whose getpid() -returns the same value for all threads in a process. But a program -compiled on Red Hat 8 and run on Red Hat 9 will by default see -getpid() returning the same value for all threads.) +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 (see NOTES below). Additionally, OpenSSL supports dynamic locks, and sometimes, some parts of OpenSSL need it for better performance. To enable this, the following @@ -133,7 +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: @@ -148,6 +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 |