Add threadsafety caveats.

p4raw-id: //depot/perl@16564

1 files changed, 10 insertions, 0 deletions

diff --git a/pod/perlthrtut.pod b/pod/perlthrtut.pod
index 8bcbf24913..6a47e10937 100644
--- a/pod/perlthrtut.pod
+++ b/pod/perlthrtut.pod
@@ -955,6 +955,16 @@ be little different than ordinary code.
 Also note that under the current implementation, shared variables
 use a little more memory and are a little slower than ordinary variables.
 
+=head1 Threadsafety of System Libraries
+
+Whether various library calls are threadsafe is outside the control
+of Perl.  Calls often suffering from not being threadsafe include
+localtime(), gmtime(), get{gr,host,net,proto,serv,pw}*(), readdir(),
+rand(), srand().  If the system Perl is compiled in has threadsafe
+variants of these calls, they will be used, but besides that, Perl is
+at the mercy of the thread safety or unsafety of the calls.  Please
+consult your C library call documentation.
+
 =head1 Conclusion
 
 A complete thread tutorial could fill a book (and has, many times),